Pidgin is a little different. Its one of the clients that can communicate on just about any network (15 "out-of-the-box", more if you use extensions/addons). But I would definitely recommend it. I use it all the time for six different networks (xfre [addon needed], AIM, GTalk, YIM, MSN, and ICQ) on my desktop and I haven't had any issues with it.
One of the other programs you are thinking about is most likely Trillian. I don't use it because it only supports YIM, ICQ, AIM, and MSN, and it isn't cross platform (I don't think).
Oh, and I just though I'd throw this out there.
Trillian:
Pidgin: