So I got an iPod Nano (6th generation) for Christmas this year, just in time since my trusty old iPod Mini started beg for retirement after almost 8 years of usage.
Since my old iPod was working like a charm all those years I expected a smooth sailing when I plugged in my new iPod Nano. Gnome recognized it correctly and mounted the device. The iPod showed up in Rhythmbox as I was used to and I started to fill it with some music. Everything worked as expected: Rhythmbox copied the music to the iPod without complaining and after unmounting the iPod and starting it -- it was emtpy. Whait, what? Why is it empty? Didn't I just... So I tried again, and again with the same result.
Half an hour later I found out that libgpod (the iPod "driver" for Linux) supports all iPods except the iPod Nano 6G. Bummer. Apparently Apple changed the algorithm to calculate the checksums of the files on the device and since that algorithm is unknown you cannot successfully write on it with free software.
That means technically this device is unusable for Linux users since iTunes doesn't run on Linux. However, there seems to be a way to use the iPod Nano with libgpod if you are trusting this guy and willing to use his binary (only!) file with libgpod (which I am not). And somehow the guys over at Spotify managed to get the iPod Nano running in their Linux client but they don't provide the code either.
Being already more than two years old, I don't have much hope that the iPod Nano will work on Linux with libgpod in the foreseeable future. On the bright side I can say the device is not totally useless as it comes with FM radio...