I tinkered with the beta, but didn't get too far along, and that was before they rewrote the interface. I've been playing it with both Cat (my fiancée) and some friends, and it's fun without being too complex. I've made some decisions regarding which abilities to implement at different times and been either pleasantly surprised or running for my virtual life, but that's part of the fun. I just wish that 8-person multiplayer was available as my gaming group now consists of five people. We solved it by playing three in one and two in another and keeping rough pace with each game with a lot of conversation via Skype. It was a little kludgey, but it worked.
I wasn't really looking forward to it originally and would have hesitated on getting it if it wasn't coming with my WoW annual pass anyway. Cat has been salivating over it for a long time and has paid enough attention to the story to pick out at least a couple of possible hooks to the expansion. I, however, was just figuring I should pick up some Logitech stock and work on other things. WoW has become a ghost town for the moment, though, and most of my remaining gaming friends are attached to it instead of the various Steam games we would play, so it's hard to do much in the way of online gaming.
I think that if WoW gets the same fine-tuning in Pandaria that D3 got with its ability system, we'll see a better game experience throughout. I expect that Project Titan will build on both extensively.
If I show up at your door, chances are you did something to bring me there.