The 2014 Toyota Prius has the interior space of a mid-size car, according to the Federal definition, and it can comfortably accommodate four adults. Three will fit in the back seat, but they'll have to stagger their shoulders--and no one will be entirely comfortable.
But as a five-door hatchback, the Prius is practical, versatile, and offers plenty of space up front for personal items, from storage cubbies and bins to trays and cup holders. The one qualification there is that the tray under the distinctive "flying buttress" console is awkward to get to without stretching around the console itself. The load bay is large enough that you won't register the battery pack sited under its floor, just behind the rear seat.
In the front compartment, the driver's seat adjusts for height--not the case in every car. But taller drivers will find the "flying buttress" center console limits knee room, and the front seats are thinly padded. Legroom in the rear is good because the front seat backs are hollowed out, and there's actually more headroom in the rear than in the front--chalk it up to the curved, domed roofline.
At steady highway speeds, the traveling experience in a Prius is pleasant--the engine is relaxed. That ends abruptly when the driver demands maximum power, though. Hard acceleration produces frequent howling as the engine runs up to its maximum speed and stays there, aided by electric power. The tradeoff of having a smaller, harder-working engine for maximum efficiency is that on hard acceleration, that engine has to work at maximum speed to provide the needed power--and you hear it. While the Prius will keep up with fast-moving traffic if you run it hard, it's much more pleasant when driven gently.
As for the materials inside the car, five years has made the textured hard-plastic surfaces less appealing. Today, even some inexpensive subcompacts offer soft-touch materials on surfaces passengers touch repeatedly. Combined with the jumble of icons, numbers, and graphs on the information displays, the Prius interior--which appeared Space Age and striking for 2010--is now starting to look dated and downmarket.