Adium is 1.2
I can't think of a better poster child for great development on the Mac than Adium. I've been using it ever since I got an Intel Mac as my old multi-protocol chat client, Fire, didn't work properly on the Intel platform. As I was looking for a solution, I noticed that Adium was looking to be the preferred solution for most Mac folks.
I downloaded it, got all my accounts into it, fiddled with the preferences to get it looking and working like I wanted, and have been happily using it ever since.
Today they released 1.2, and the release notes indicate a ton of bug fixes and localization changes. Not that I had that many problems with it before, but it's nice that they are continuing to work on it. If you need something like this, get it - you won't be sorry.