The ic602 and V950 have exterior "smart key" functionality. The square button will key up recent calls and the volume rocker scrolls through the list. The speaker button will also dial either the last number you called or the one highlighted.

I agree that Legacy Nextel phones still have the most customizable UI's, although the one on the above mentioned phones is okay.

The one customizable feature from the Sprint side that didn't make it over is the "roam only" option on the V950. It's available on the 602, but rarely will you find an available PCS network to use it on.