Okay, two things from the off
1) I LOVE this thing
2) Its a pain in the backside to get it going
unwrap the AppleTV and you'll see it has no cable, so rush out and buy an HDMI. Come back, notice the power cable has a shaver style plug on it. Rush out, argue with an electronics bloke about the wisdom of putting a 2.5amp glass fuse in a shaver plug converter. Come home, plug it in, lose the will to live.
Then it all whirrs into life and starts downloading your music collection....
.... and 3 hours later (well best guess as I just went out and left it to it!) you're ready to go!
Once its plugged in and ready to rock it's a breeze. Control it via your funky i-pod style remote and it will play your playlists, videos etc. just like an i-pod. Only downer is that there's no visualiser, which I would have really liked to see, though it will do a funky layered slideshow of all your pictures while your tunes play out.
Other than that, simple to use, great sound, updates automaticaly, SUPERB product, once you've got it set up. Best consider it to cost at least a tenner more than the asking price by the time you're done though!
EDIT: Seems to have updated its firmware and now installs trailers for all the latest movies and a whole section of YouTube videos overnight. Crazy stuff, pretty interesting (movie trailers are great in HD) but I'm slightly worried about it going off and doing all this stuff without me telling it to! No problems yet though.