Just after the Apple TV was released I purchased one.
I am really happy with it. But being here in Australia and iTunes doesn't have TV shows available which is disappointing since the Free to air channels are **CRAP** and just screw with all the descent shows and really make it frustrating to watch. (Well back on track) So I have hacked my AppleTV so that I can get my content from my computer in the office.
Many people have complained about the size of the 40G hard drive and even with Apple releasing a version with a 120G hard drive and am not really worried about the size. and I just stream the content from other systems. Even with just a 802.11g network it still works really well and I have not problems with rebuffering.
My biggest problem I have is with the sync'ing being so slow!!! I like to sync all my video pod casts and music to the hard drive. But it always takes soooo long to the content to arrive on the AppleTV, and usually end up sync'ing it manually.
Since the AppleTV and iTunes system are on the same network my expectation is that the as soon as a podcast or new music that needs to copied to the AppleTV should be pushed there immediately, but sadly it doesn't
If I needed to get one thing changed on the AppleTV is that I would add a push sync service to iTunes to deliver content to the appleTV much faster.
Other than that I love my AppleTV and want to see it go much further.