I believe it works for US/Canada only...
I thought about this too and have tried it. It works, HOWEVER, the stupid AIM app LOVES to disconnect you and ignore incoming msgs if you're not in the app, so until the Notification service is up and running in (sept?) you can't really rely upon it for receiving TXT msgs...
I plan to go this route in Sept however and drop the TXT msging rip-off plan...