OK guys, I've put 0.28 up on my site.
http://www.pier13.com/rioplay/

Changes:
- Streaming audio should now play back without gaps
- No longer starts playing automatically when turned on. It's still set to the last song playing, though.
- Supports sample rates other than 44.1kHz
- Display backlight goes off after 30 seconds of no keypresses
- Added a logging mechanism which logs useful information about what's going on. This log can be accessed by pointing your web browser at the IP address of the Rio.

I've played streams of 8kHz, 24kHz, and 32kHz and they all play back at the right speed. However, at 24 and 32, there's a bit of a buzzing sound. I don't know if this is a bug or merely a side effect of resampling from those rates. I used the resampling code from resample.c in the MAD distribution (thanks Andy for pointing that out).

Let me know how it works out for you all. I hope it solves some of the problems people were having.