I can mount my Xoom in linux using libmtp and mtpfs, however, it's slow, kludgy, and generally feels like it will flake out at any moment. Additionally, even when it's mounted, I can't seem to copy music across properly; it doesn't keep the folder structure. In fact, the directories are created and any non audio files are copied across fine, but every mp3/audio file is flatly dropped into the Music directory.
I tried to copy some music onto it from my fiancee's windows xp laptop and it worked ok (though the album art didn't appear).
The move away from mass storage to MTP is a massive disappointment for me. Mass storage has always been a big selling point for me when purchasing a device and for Google to switch to using a Windows specific protocol and consider it cross platform is a big letdown. MTP on mac requires a special app and on linux, support is dire, certainly for anything more complex than simply pulling images from a camera.