There is a ton of stuff on the internets all about this. Biggest difference between Beta 1 and Beta 2 is that Beta 1 was a "developer release" while this version is supposed to be ready for everyday. Obviously not RTM so there are still bugs to be expected, but it seems cool.
The pr0n mode seems popular
I personally like the colors on the tabs to show you the groups of tabs and how you can close a group of tabs with a single click - just wish you could close all other tabs except for the group