I have been driving my Insight for close to 5 years. Overall, it has performed very well-even when the battery pack unexpectedly failed recently (it was 6 years old), I had no problems getting back on the road in about 2 weeks, completely covered by Honda's warranty. I've averaged over 54 mpg, mostly in short-trip, city driving in Michigan, where the cold winters reduce mileage quite a bit. However in the summer, I easily average 60 mpg or more.
The interior design is sharp and solid- - nothing feels cheaply made. Comfort is good even on long trips. The exterior has a unique "Buck Rogers" look which never fails to get the attention of other drivers.
A better stereo and the option of a sunroof would be helpful.