Ask TUAW: What's your favorite multi-network IM client?

TUAW reader varun submitted a good question for an Ask TUAW session on the topic of multi-network chat clients. varun has tried out the likes of Fire, Adium and Proteus, but hasn't come up with a compelling reason to use one over the other.

I thought this would be a nice opportunity to ask you readers to sound off on which multi-network IM client you prefer, and why. When commenting, be sure to mention how the client fits into your workflow, what you like about it and why. The more clients you can bring to the table above and beyond the ones already mentioned, the better.

So what say you, TUAW readers? What is your favorite multi-network IM client, and why?