Hardware wise, nothing. Software wise there is a bunch! Let me point out some things that really mattered to me in these updates:
When I first bought my iPod Nano, that was the software (OS) version that came with it. I never really used that version, since ever since I’ve plugged my iPod on my Mac for the first time I downloaded the software update right away. But I heard that that version didn’t allowed you to shutdown the iPod, just put it to sleep, thus, lessening the battery life, very, VERY annoying.
Much better. Now you can shutdown instead of just put it to sleep. Battery life is not that great. Track order by albums is messed up after syncing with iTunes, it’s a pain in the ass to fix.
Much, much, MUCH better. It seemed to me that the battery life now last longer. Syncing your playlist now works flawlessly, the track order by albums is kept. New interface “coverflow-like” (the old one is still available), but I prefer the new one.
New Sports App features.
I few new wallpapers. A lot of clock themes. A lot. Some really cool, very geeky, others very elegant and traditional, some very modern, others a little weird, like the Mikey and Minni Mouse ones…
And… that’s about it. I feel that the experience of using the iPod became more smooth, more solid with these updates. Nice : )