i left my screensaver on for about 30 minutes with an away message up in iChat AV, and to my surprise when i got back i was asked if i wanted to be signed back in after being away for that long, this is a pretty small feature but it was a pleasant surprise to find
iChat AV has several new things like that. There is one thing I really hate though: if you set an away message, and get a message, it doesn't register when you return and if you try to open a new IM with that person, it doesn't work, says something a long the lines of "You already have an open IM session with this person". You have to sign off and then back on to IM them. Pretty annoying, but...
Same thing happenns to me, and I can't STAND it. Not a big fan of the fact that I can't add FULL address book info (phone #, address, birthday) through the iChat user info window....I have to go and open Address Book to do it.