I read yakko's rant about IM clients and decided that I was curious enough to make a poll about this very topic, to see what you use. This is especially interesting to me as I've been working these last few weeks to organize my IM contact list.
Edit 1430: I had a poll here, but the goddamn poll builder shit itself and died a horrible death. I'll come back to this.
I'm also curious -- if you use a "hybrid" or "multi-client" IM program, what do you use? On the Windows side I used to be a pretty big fan of Trillian but it's become insanely bloated. No IM client should take two minutes to start on an AMD64 machine with two gigs of ram! Insult to injury is that since the new version came out I would have to re-register if I want to use any of the features I'm actually interested. This has generally forced me to use Gaim as it's relatively cross-client and lightweight.
On the OSX side I use the super-sexy Adium for my MacBook. It is lightweight and fast, highly configurable, talks to damn near any IM platform you can think of (even client protocols I didn't know existed) and integrates with other parts of my OSX environment like the built-in address book.