I'll chime in with exactly two cents.

1. I find iTunes 7+ (not iTunes 6 or any other version) to be the best music management and display software I've ever used or have had the opportunity to research/read about. I've got about 80GB in it right now. *not that iTunes doesn't have issues or things I'd like to alter.

2. When I looked into RockBox (about 6-12 months ago) it looked very unpolished and for the couple of music formats and features gained, you'd lose a huge ton of functionality and user interface polish. Maybe it's better suited to players that come with craptastic firmware, but for the iPod it just seemed like a downgrade. * not that iPod's firmware doesn't have some issues of its own, including navigation that could be done better.