Microsoft also went through a stint of trying to make their MSN thing compatible with AIM's Oscar protocol. IIRC, during the height of that battle there would be several new revisions of MSN released every day because AOL would block one and MS would find a new way around it. And since I somehow doubt Cerellean or whatever their name is has quite the development capabilities of Microsoft, I think Trillian will probably fail and die if AOL starts really trying to block them again.
Personally, I just use regular old AIM anyway. I dunno, I just never got into Trillian like most people. I really did try, i've had it installed several different times and tried to make myself use it, but I guess I'm just afraid of change or something dumb like that. So it's always back to regular AIM after a day or two.
---Jamin