Just rented a Prius yesterday. A few observations:

1. The split rear window was annoying, and made me feel like my rearview mirror was never in correct position. Also, in the rain the bottom section of the rear window below the wiper was never clear.
2. Several features made me feel like I was driving a goofy toy car...the steering wheel seemed small, the dorky little joystick shifter on the dash, the tacky audible chirp sound when you use the touch screen, the claxon when reversing, and the lack of any visible hood when looking out the windshieild.
3. The dash gauges were poorly designed. They are on top of the dash toward the rear near the windshield, so that the display is several feet further from your face than the Camry.
4. There was considerably more wind noise and engine acceleration noise.
5. The stereo was considerably poorer in design and accoustics than the Camry JBL.
6. It was easy to get 50-51 mpg.
7. Backseat is very big for the size of the car. Not as big as the Camry but very practical nonetheless.
8. Handling and acceleration weren't noticeably better or worse than the Camry.

Bottom line -- if Toyota offered a loaded, more deluxe version with better interior, more sound insulation, better dash design, without the split rear window, I would buy it. But I would not want the current model just for 15 more mpg. It confirmed how much I like my Camry.