First, the implementation, on a UI level, bothers me. The app, which, right now, you cannot opt out off, installs a toolbar along the bottom of your browser window. Cool, more clutter. Thanks.
Also, this really needs to be optional. If I’m on the site up to no good, I don’t want my dumb friends bombarding me with “YO BIG PAPI WHAT R U UP 2?” Always assume I’m not up to anything, thanks.
The app itself, and the chat interface, isn’t bad at all. Very simple. You double click someone’s name and a Web 2.0-approved window appears. Then you chat. That’s it. If you’re in another tab while someone IMs you, the title on the Facebook tab changes to say, “Hey you’ve got a message,” much like Meebo does.
On the whole, I guess the app is handy. But I do wonder, if you’re really friends with the person, wouldn’t you have their AIM/MSN screen name already?