Jeff, on PortalPlayer targets (iPods, Sansas, and a few others) the major missing functionality is a native USB mode, though you can easily dual-boot to transfer files or sync to iTunes or what have you.
You can't play DRM'd tunes, either, but that's something impossible to implement, really.
Rockbox runs on quite a few targets with more in the works; check out the main page for the full listing of Rockbox targets :)
Jeff, on PortalPlayer targets (iPods, Sansas, and a few others) the major missing functionality is a native USB mode, though you can easily dual-boot to transfer files or sync to iTunes or what have you.
You can't play DRM'd tunes, either, but that's something impossible to implement, really.
Rockbox runs on quite a few targets with more in the works; check out the main page for the full listing of Rockbox targets :)