I've recently installed Pidgin (used to be called Gaim). It has *tabs*.

Conversations can be grouped in different windows or dragged and dropped
to create any combo of individual windows and conversations. I guess I'm
kind of enamored with this because of the quantity of chat windows that
I can have running during the course of a day.

BUT, the drawback is that it doesn't do Chat rooms or handle outgoing
broadcasts so its not really a replacement for the native client.

Anybody else have ideas that should be submitted as a feature request?