Yeah, I use it. It's a little better than the MSN-messenger integrated thing because it allows group chats. I haven't tried using the features you have to pay for, but it looks pretty cheap, especially for international calls.
mbonwick, you could just ask your friends for answers to your homework with a normal instant messenger.
I hate mobile phones and don't own one. I wish there was free city-wide Wi-Fi and a free internet telephony service. That would really get people communicating. Instead people have to get mobile phones and some spend far too much time and money texting and calling people, much to the delight of the phone companies. :read: