This review is going to be a little short because I didn't spend too much time with the Prius Prime and didn't take any pictures.
What is it?
The Prius Prime is a concept car. Obviously it's mass produced, but what I really mean is that it's a car that sells, reinforces, and is designed around a vision for The Driver Of The Future. Without this concept, the Prius Prime would be yet another hybrid to be bought and driven apathetically, with a halfhearted excuse of "well it's good on gas..." to justify its purchase. Fortunately, what really sets the Prius Prime apart from its competitors (being Toyota's top plug in hybrid model) is its ideology. If you drive one, you'll adopt that ideology soon enough. It's clever like that.
How does it drive?
Why do we even care? It's a Prius-who cares how it drives? If you want a fun Toyota hatchback buy a first-gen Matrix. We're not here for fun.
For starters, it has fully independent suspension, which is a plus. You don't notice it, though; it's there to shunt the Prime's 3300-odd pound curb weight around corners, and it does the job admirably. For how heavy it is, the Prime corners like a smaller car, though its weight is impossible to ignore. This actually acts to its advantage on rough roads, helping to attenuate shocks. Fortunately, Toyota seems to have put yeoman's work into lightening the Prius Prime already (I recall reading about aluminum hoods and carbon fiber rear gates and the like), and as such, the Prius Prime is seeems to be lighter than might be expected from its market segment. Overall, the Prius Prime does a good job of hauling its battery mass through turns, and never feels like it rolls unduly.
If I recall correctly, the Prius Prime's 1.8L Atkinson-cycle engine is rated for about 120hp and 109lb-ft of torque, which seems remarkably low both for its size and for the market segment, but remember that matching the market segment number for number isn't the Prius Prime's goal: It aims to move the goalposts, rather than throw the farthest. By the quoted numbers, the powerplant doesn't seem to impressive, and I agree that without the electric motor, it isn't. However, the motor has extremely impressive torque (as expected, it's a motor) and makes acceleration very responsive to throttle inputs, at least when in the vehicle's "Power Mode." Power Mode seems to boost steering assist gain and quicken acceleration response, while the other two options, Normal and Eco, seem to soften both accelerator and steering respectively. This is expected, and nobody is driving this car for sensitive handling anyways.
The transmission does not have a low gear setting or a fake manual mode. You take the ratios it gives you and you thank it for them, and the aggressive traction control system figures everything out. The powertrain of this car is smarter than you. By a long shot. Putting it in neutral and putting your foot down doesn't result in fiesty four-cylinder buzz from under the hood, instead, the car gives you an angry beep and tells you to shift to drive if you want to go anywhere. It doesn't even rev the engine for your trouble. It might as well just give you directions to the nearest Dodge dealership and tell you to trade it in if you want to clown around. On the highways, the car gets great mileage, and is surprisingly quiet; the steering assistance seems too soft and loose at slower speeds but is very responsive at motorway speeds: this car doesn't feel heavy or sluggish when you're cruising on the interstate. Rather, the ample torque from the electric motor makes passing easy (get used to clicking between Power and Normal modes though), and the taut steering makes lane changes quick and easy. Between the great mileage and easy highway driving, the Prius Prime should be a good car for both long commutes and road trips.
The weak parts of the user experience are the complicated controls, cluttered dashboard, and clumsy infotainment system. There are too many menu buttons on the steering wheel and few of them are marked intelligibly (you press the MODE button to mute the audio, but only sometimes?), and there are several different display menus and settings on the gauge cluster, which is a narrow horizontal screen at the middle of the dashboard. The driver can choose between a massive variety of information for the gauge cluster and little of it seems to be of use, but then again, what would a Prius be without futuristic (and questionably well animated) displays? As a driver of more conventional, and older, cars, the Prius Prime's gauge cluster is difficult to make sense of, and most of its abundance of information isn't too useful to me. Fortunately for the long-term Prius Prime driver, many of these infographics are perfect for tuning your driving style for the best mileage and most regenerative braking power recovery. The infotainment screen is loaded with functionality but is clumsy and distracting to use; the latter aspect is of course unavoidable for infotainment systems that rely on huge screens. The satnav interface has to be a decade old and doesn't work amazingly well; it was fine in the 2010 SRX, but that was because smartphone navigation was primitive at best. Modern smartphone navigation is far and away better than the Prius Prime's system. Most of the rest of the infotainment software is fine, but suffers from a disappointing touchscreen and menu design that doesn't exactly delight.
Fortunately, driving-critical controls like the drive mode buttons and that classic Prius shifter are easy to use; the user can toggle between EV and hybrid driving as well as the three power management modes with buttons that are close to her fingertips, at least if her arm is on the center console armrest; this is actually extremely well placed and is very comfortable. With the generously sized mirrors and backup camera, the driver doesn't really have to move too much at all for normal driving, as practically everything is at the fingertips. I would appreciate the drive mode buttons being placed on piano-like keys, as that would make locating and using them even quicker, but their implementation makes sense. The Prius Prime is quite pleasing ergonomically, and for any normal driver, should work absolutely fine.
Overall, the Prius Prime feels like a completely normal car. The weight of the hybrid system is offset by a good suspension, huge torque from the motor, and some clever weight reduction strategies, and it doesn't feel either entirely numb or extremely jittery. The fact that it drives so unremarkably however, is the point: its normal driving experience is a blank slate that you are trained to develop.
A Prius Prime owner's driving style will adapt to the way the car treats them. Acceleration, braking, and cruising are graded for smoothness and energy recovery; multiple informational menus tell the driver how to maintain or increase their speed with the least energy possible, and the color scheme of the speedometer changes for Power/Eco/Normal Modes to let the driver know they're wasting energy (or not). Does all this work? Of course it does! Humans love praise, we love appreciation, and we love to see the numbers go up. So be good and learn quick, and your Prius will score you better, and you will be rewarded with nice high numbers and good gas mileage. The Prius Prime's user experience is the ultimate extension of the social engineering fuel gauge of many conventionally powered cars, where the first 3/4 go by like that, but the last quarter lasts ages, so as to make you think "oh no, I need to hit the pump" without the car directly telling you. The Prius Prime praises you for easy acceleration and constantly slightly riding the brake when coasting (for regenerative energy recovery, of course), and dings your score for excessive acceleration and braking. When you get a Prius Prime, you don't just buy into the plug in hybrid energy ecosystem: you buy into the behaviors that support that ecosystem. Your Prime will train you to drive it better, and you'll thank it for the privilege.
What does it mean? Who is it for?
Ultimately how this car drives and what it does materially doesn't matter so much. These are framing for the heart of the point that Toyota is making with this car: When you buy a Prius Prime, you buy into the Hybrid Lifestyle, but you also buy into a postmodern, eco-friendly version of the American Dream, where the promise of a big car and the open road are still there, even when gas hits $4 and your town never gets snow any more. It's fine that the Prime feels a little weird at lower speeds; when you're in a town at lights and such, you don't notice how it drives, since you're just trying to get somewhere. On the highway though, it becomes a wholly different beast, and it's on the crowning glory of American transportation (finished of course during the years when Johnson's Great Society vision was still alive) that the Prius Prime really comes alive. The electric motor's torque and responsiveness make passing a breeze, the taut steering makes lane keeping low effort, and the efficient engine and quiet cabin make longer trips both cheap and comfortable. With a Prius Prime, you have a big car that looks flashy, impresses the neighbors, and drives easy: that's what the American Dream is! It's the aesthetic of Making It, and what better symbol to show that you've Made It than a futuristic family car that you can commute to work in without burning any gas? In a Prius Prime, you feel both comfortable and sophisticated plugging your car in at a charging station, or hearing the (specially tuned for your enjoyment) whine as you regeneratively brake your way down a long hill, or feeling the shove of the electric motor as you accelerate out of a sweeping interstate curve. A Prius Prime envisions a future where cars aren't obsolete, they're just different: maybe they do most of the work of driving now, but they're still cars, and that's what matters more than anything else. The Prius Prime is Toyota's vision for the car of the future, not as they are in styling blanks and concept art, but as they are putting rubber on the road and taking the kid to fencing practice. It's no mistake that Toyota's hydrogen vehicle is called the Mirai.
The Prius Prime keeps the dream of a car to aspire to alive, in a day and age when public confidence in gasoline and cars in general is starting to weaken. The Prime promises that the future can be just like the good old days, only sustainable this time. Maybe huge change won't come after all, maybe everything will be okay. Maybe you can still hop into a big, quiet car and seek the open road and the horizon beyond it. Maybe riding off into the sunset can be eco-friendly after all, and your car will be there with you every step of the way, with its lane departure warnings, automatic headlights, and driving style scores.