2012 Toyota Prius c Three 4dr Hatchback (1.5L 4cyl gas/electric hybrid CVT)
Here's where my experience seems to differ from what you might expect:
1. Power (i.e. torque) is just fine. I'm a pretty aggressive driver and when I need to go 80 in metro traffic it gets the job done. I have a family member with a 3.0L BMW Z4 and I can't say I particularly miss the acceleration when I'm back in the "c".
2. I'm just out of the 2k mi break-in period but based on the computer and some validation from the gas pump I'm getting ~45mpg rather than the 50mpg the EPA says and the 60mpg the enthusiasts brag about. You *can* get 50mpg+ but it seems you'll need to really commit to the pulse and glide method (and obeying the highway speed limit) to get this.
Bluetooth for music
Tray for smartphones
Mileage (obviously) and enough feedback for obsessives to improve their performance
Dimensions make it easy to park
Higher power USB to allow charging iPads
Lithium ion batteries to allow longer EV mode cruising, better mileage; plug in option
Fully flat fold-down back seats
I have the Prius hatchback, and what I found was that to get the EPA mileage or higher you have to prevent flooring the accelerator. Try keeping the bar within half inch above the mid-line, and you will be surprised on the improvement.