And just in time! I wanted to use the new Ajax effects in a project I've been working on, but not until they were final. That time has come.
Ajax aside, Routes (a stunning feature) have been upgraded to provide a sevenfold speed increase, and the swathe of render_ methods have been consolidated. Tobias provides an overview of this change.
Conditional validations are new too. The given example is very good; only validate a password for existance if it's a new password... otherwise we can assume it exists.
It's the little things that make me so happy.