My friend picked up the 5gig one from the UCLA store for like 269 (student price) He is using Ephpod. Hee was using macopener and got a stable 1.5mb/s transfer rate. He read about macdrive. He tried it out and found that i had speeds from 4.5-7mb/sec. YMMV He is using win2k. I think it's a sic little toy, and if I was in the market for an mp3 player, I'd get an IPod in a heartbeat.
A guy at work picked up the Rio Riot and it's ALOT bigger and heavier. I didn't like the interface. The IPod has a clean interface, easy to use buttons, plus the backlighting on the screen was much cooler than the Riot. Granted the riot is 20gb compared to 5/10.