I know Alpha 2 of Deer Park has been out for over month, but I just tried it a couple of days ago. I have to say that it seems much faster especially when using the “Back” and “Forward” buttons. It is supposed to have “Better support for Mac OS X” which is a definite positive. I was also surprised that a number of the extensions I use still worked with it. The only one that didn’t was Bookmarks Synchronizer, but I use Simpy now anyway.