I am a new owner of a Soundbridge, and I am love with the thing. It is simple to use, works well, everything I could want in a network MP3 player.
Here is my fantasy Roku machine:
Take the SoundBridge. Combine with the Netflix box. Add ability to decode video streams sent from my local network, like MediaMVP.
*Streamed MPEG, DivX, etc.
*YouTube, Break, other Flash based services
*On board display for MP3, text info
*TV display for video, graphical browsing of music library
*TV display shows album art when MP3 is streaming