The 2013 Honda Insight is far from the roomiest subcompact hatchback on the market, handicapped by a body shaped for minimum aerodynamic drag and the need to house a high-voltage battery pack under the rear load bay. (The Toyota Prius C, its newest competitor, manages to get both a gas tank and a battery pack under the rear seat--giving it a full-depth load bay.)
The Insight is comfortable enough in front; the front seat cushions are a touch short, with grippy mesh fabric that holds well, and the headroom for front-seat occupants is generous. But the cramped rear seat offers very little headroom for two adults, a consequence of the drooping roofline. Last year, Honda reshaped the rear seat cushions and "sculpted" the headliner to increase rear headroom by more than half an inch--and every half-inch counts back there. Three kids can fit into the rear in a pinch.
Open the rear hatch, and you'll find 15.9 cubic feet of cargo space. That's a decent amount, but it's compromised by a high load floor and rear seatbacks that don't fold flat despite a 60/40 split, meaning the load floor isn't flat either. That contrasts vividly with the uber-flexible Honda Fit just a car or two over on the showroom floor.
While the recent Honda Civic was a disappointment for its interior materials, the Insight is about average for subcompacts. It has few soft-touch surfaces, but the hard plastics expanses are pleasantly grained and all the parts seem to be fastened together well. The doors are tinny when closed hard, and it's one of many signs that Honda has made every effort to cut weight to a minimum--resulting in remarkably flimsy materials for things like the headliner.
Ride quality in the 2013 Insight is good, despite a short 100-inch wheelbase, and the car is quiet under most circumstances. The one exception is spirited driving, when drivers and passengers will find that demanding maximum power from the engine makes it remarkably raucous, with a loud howl when the throttle is mashed.