The key improvement with this update is that it gives you the option to change the sliding information drawer into a window (which is pretty important if you're working on a 12-inch iBook). The read-me talks about other performance issues, and I think at least one of them might be that it gives you the option to disable alarms when iCal is not running (...or was that there before?).
Still room for improvement (e.g. still can't set the time in a to do without calculation from midnight ), but detachable window is fine. If you create a kinda square event info window in the bottom right corner of a PB12, you can leave the to dos on all the time and view the extra info by pressing i. Neat.
i remember double-clicking on an event... and having trouble finding where the INFO window was... I figured out that because I had my iCal window maximized, I couldn't see the drawer on the right.