I am not sure that I am not the worst possible person to give a beta invite to. Yesterday when I got one I was thrilled and couldn't resist installing it right away but when it comes down to betas I am reluctant with this one, as I was with Mists, to actually step into the new continent.
On the one hand I want to desperately, I want to go and see the new shiny zones and the critters and the quests so badly I can almost taste it. I want to help finding the bugs and things so that when it does go live it will be amazing.
On the other hand I'll do all that content many times when it goes live and I am very reluctant to take that shiny newness away from myself before it actually launches. But I've played with it some, gone in and looked at the character creator for the models that have been updated, and made myself a few characters to try out.
And so far dipping my toes in that's all I've done: Taken Kaarras to the Timeless Isle to see how he stacks up against a much better geared ret paladin in live. (About like I'd expect, really, though without meters and with squished numbers I'm going purely on how it feels to kill things.) I'm still so tempted to look at the new things, just poke my head in the door. On the other hand once I see it I can't get the newness back. So just at the moment I'm seeing how many times I can crash the game by rearranging my action bars (twice so far).