When I am bored I play with it with the 3 people I know that have an iPhone4... When they allow things like skype, using it on 3g, or connect to ichat... I will use it almost daily.
Honestly I haven't used it much since I only have 3 friends with iPhone 4's but the best use for it so far is That it uses wifi. I have a friend who spends all of his time in his basement and usually I can never reach him but now I can call him with FaceTime! Lol
I was figuring most people hadn't had a chance to use it. Wonder if there's a way that iChat AV could get it integrated. Not sure how you'll do that without a phone number on your Mac though.
I like it. I've had the phone for less than a month and I've used it 8 or 9 times. One of the calls was over a half hour with my friend. We were just BSing and showing eachother what we were doing. We actually tried jamming because he was playin guitar and I went on my drums. Let's just say it didn't work LOL. plus that 35 minute call only used less than 20% of my battery. To me that's pretty impressive.