Poll: Best IM solution?

So say your company has been chugging along without an instant messaging policy. Folks have been using whatever they're comfortable with. This has led to "You're on IRC, I'm on AIM, she's on Gtalk." problems. Things like Pidgin, Colloquy, and Trillian have made it less of an issue, but it would be nice to have SOME policy in place.

Normally, I'd say "Go jabber, run your own server, be happy", but Jabber / GTalk has the fatal flaw (as far as I can tell) of having no chat room / multichat functionality.

So. What would you recommend? The chat room thing is important, but not a deal breaker. Persistent rooms would be nice :)

[Poll #1637469]