I had a sony ericsson 550 which was great as both an fm radio and an mp3 player (only 256 mb, non-upgradeable). The battery life was decent around 3 hours of continuous music or 3 days of talking + radio while commuting (by bike). The swivel design was terrible though. Anytime it swiveled a little, it unlocked the phone which was a major problem and there were no carrying cases that fit it well (even the ones designed for it had issues). The biggest problem however was that I wore out the swivel on two phones in 5 months. After one month, I could feel that the joint was not nearly as tight as it started out and by two months they were nearly falling apart. Neither made it to three months.
Cliffs
I loved the features of the 550
batt time was ok but could be much better
swivel is a poor design and must be handled like a piece of China.