I have an older 2GB iPod Shuffle and decided to test it out with Ubuntu Netbook Remix 10.04 on my little Acer Aspire 532H. I believe this is the 2nd generation iPod, the one with the little clip on the back.
The iPod seems to work very well when you plug it into the USB port. When the iPod is plugged into the little Acer's USB port, Rhythmbox starts right up and recognized the iPod and its music files that I had imported from another PC. I then proceeded to move files back and forth and it worked well. Files delete in a flash, but it takes a little longer to upload files from the PC, unto the iPod.
I could also play music from the iPod through the PC speakers using Rhythmbox
I suppose there also would be no problems using it to carry music that is downloaded from Ubuntu One Music. I have not purchased anything from Ubuntu One Music yet, but the seem to have a good selection of music.
Rhythmbox hung once when I removed the iPod without using the "eject" feature within the Rhythymbox software. This feature can be found by right clicking on the iPod icon within Rhythmbox and selecting "eject." I was then greeted with a little green light on my iPod that said it was fully charged and ready to go! If the little light is flashing yellow on your iPod, remember to "eject" it from Rhythmbox before you disconnect, so the sync can properly finish.