The new Yahoo! Messenger (v6.0) looks really impressive. Some of the new features are integrated LAUNCHcast Radio, Games, Avatars, Audibles, Stealth settings etc. Yahoo address book synchronization with Messenger is neat too.
However, I still support the idea of an integrated multi-protocol IM software like Trillian, Giam (my fav) and Miranda. Who would want to install 5 different IM’s? One single tool doing the job is good enough for me, and having it on a USB memory drive stick provides even more mobility.