I’ve just decided to give Adium X a try — had no idea about it, till I saw it in Darwin Ports listing in aqua category. It feels very solid — I’d say more so than Fire, albeit it is obviously very subjective statement. There sure seems to have been more thought put into the UI, etc.
Both of them beat Psi tops down as far as UI goes — but that’s to be expected, considering that Psi is a QT application that is taking advantage of QT being available on Mac as well as on most UNIX flavors and Windows. The look is sort of ok — from a distance it may pass for a Cocoa app, but not once you get close, let alone personal.
What is regretful in Adium, is lack of GnuPG support. I’d switch over to it today, had it had GnuPG at core or via a plugin. It also seems like this whole topic is bo-bo with developers… Strange.