If we go back to the beginning, I dumped AOL's AIM client because the mouse-over ads pissed me off.
I've got iChat on my Mac, and it gets me into AIM and LJTalk (jabber) chat servers.
I've got Trillian on my Windows laptop, and it gets me into AIM and Yahoo IM.
Now I hardly use Yahoo IM, because during the day I'm on the Mac, and because I've got a pretty full buddy list on AIM already. I wouldn't mind being able to get into LJChat from the Windows machine, but to do that through Trillian would involve paying for the "Pro" edition of the software.
What unified IM clients for Windows are out there that provide good AIM and Jabber support and are free?