I do love my iPod nano, its a great piece of technology but it does have its downsides.
It includes tons of features on it that I'll never use, perhaps Apple should take this into account for next time, maybe they should sell iPods without all the pointless features and maybe they'd be alot cheaper.
My main concern is how much this thing freezes up.
My old iPod mini only ever froze once.
The nano will freeze up alot, especially if you go to play a song you've just uploaded to it, so you'll find yourself having to reboot it. It can be really annoying a times.
On a posative note; the battery life is pretty good. If you charge it on a regular basis (keeping the Li-on active) and letting it drain out once a month to keep the battery gauge acurate (remember to charge it up immediatly after its empty as prolonged emptiness of the battery will damage it)
I also strongly suggest to buy a skin for it, as it will protect it from the daily knocks and bumps. Especially the screen.