Please don't recommend Pidgin; Pidgin is the IE6 of the chat world… it's terrible, it holds back the rest of the world, and it just won't die (although I know this was in response to the question; just sayin')
I know, right? They've been working on their v3 release for centuries now, but it looks like it's another few centuries away. It's a shame, because it's a really good client. I just wish development was faster.
So what desktop client (Win/Linux) do you recommend instead? (I use pidgin, but mostly because that's what I've always used, it has quite a few weaknesses)