I'm also interested in this, I have most of my music loaded in RhythmBox from my iTunes library on my NTFS formatted (read-only) Windows drive. RhythmBox brings I my MP3s, but not my AAC (.m4a) files. But most of all, I'd like access to my AirPort Express.
I'm also primarily a Mac user, and I'm very close to having my PC default to Ubuntu. I just need to get a bit more familliar with Wine for those one or two apps that I need. iTunes would be a big plus too.