I don't like Trillian 3.. I loved Trillian 2. It's faster, less bloat, and more stable in my opinion. Since the recent problem where you can't use ICQ at all with Trillian 2.x however, and they haven't updated.. I'm trying Miranda IM out. It's very light-weight, and supports tabs. I'm like it a lot.
http://www.miranda-im.org/