Lots of different opinions here. Obviously, once it's out we'll know real-world performance.
I just got my email this week from Amazon that they're accepting pre-orders, put mine in.
I want to experience the new AF and get a look at the RAW files. If I'm not happy, I can sell it for, probably, a $150 loss, and I'll gladly pay $150 for an unlimited rental. Plus, it could turn out to be a smokin' winner.