I tried the symbian version of MSN Messenger
I liked the functionality - almost as good as on the desktop.
Just a couple of problems, though. It puts hotmail in your messaging app, msn messenger contacts in your address book. Oh, and in the E90 it messes up the widescreen properties of those two apps as well, making Andrew Orlowski's favourite device look craptastic.
I'll stick with Slick. The name says it all!