Using your phone as your mp3 player while you work out sucks. It gets sweaty and gross and you have to carry it around the rest of the day smelling like your armpit. No thanks. Give me a sweat-proof one like the new Sports Walkman.
Sony's new waterproof mp3 player looks kind of amazing. It gets a reported 8 hours of battery life, which is cool if you're running a couple of marathons or something, but the more useful bit is that it gets an hour of battery life out of just three minutes of charging. It syncs with iTunes or the PS3, or you can just drag and dump a bunch of songs onto it. It only has a 2GB/4GB capacity (good for ~500/1000 songs), which kind of sucks, but should be enough for trips to the gym. They'll run for $60/80 when they come out in August. [Sony]