As can be seen from the very long change list, this is a pretty big upgrade that adds lots of features, fixes lots of bugs, and makes a lot of UI refinements. One of my favorite new features is the upgraded MSN library, which, among other changes, adds support for personal messages.

Still looking forward to a/v features being added, and the documentation could stand a lot of improvement (yes, I'm one of those folks who actually reads the docs...) but other than that, Adium is great.