Dual Spec: Huzzah! Been waiting for this for ages. Seems to work. Haven't really put it through its paces yet. It does everything it needs to, though - swaps out your talents, glyphs, action bars and key bindings. It takes 10 seconds to do while you're out of combat. Wow. This is looking to be an amazing addition to the game.
New Talent UI: Never again to waste 50g on a mis-click! You get a 'learn' button when you respec, so that you can fiddle your talents until they're right.
Gear Sets: While this is almost certainly a welcome addition for people not already using a UI mod with similar features, I'm not going to get rid of Outfitter. My very brief experience with it was that it was buggy and hard to use. It was almost guaranteed to mess up my weapons and/or shield - especially when I used it in conjunction with dual spec. Oh yes - fun dual spec foible in the current PTR: if a warrior swaps from a Fury/TG spec to prot... you'll still have your two huge two-handers equipped while you're prot. I'm assuming this will be fixed, but it was funny. One issue with this feature is that it allows you to select an icon... but it doesn't have any process for choosing sensible defaults. Outfitter lets me choose an icon for my outfits by selecting a piece of gear in that outfit.
Still to come: new quest tracking UI. I enabled it, but haven't spent any time questing yet.