I spent a week with one, at the end of which I returned it to the store as defective. The AF system is appaulingly bad. The speed is bad enough but it also has a tendancy to lock onto the background every so often rather than the active focus point (as Chris mentioned).
The build quality is amongst the best I've seen. Image quality is superb and rivals anything I've seen on a crop. It certainly stands up against the D7000 both in IQ and ISO performance upto 3200.
The lens will be limiting for those who primarily use zooms but the 35mm field of view is perfect for what this camera is. If you like shallow depth of field and don't like to get up close and personal then this isn't the camera for you. Although you'd have the same problem with any crop camera and a 35mm lens.
My advice would be this:
Great second camera for carrying with you if image quality is more important that consistent or speedy AF.
* This can be less of an issue if you start to look at pre-focusing your shots and shooting old style.
Poor camera if it's going to be your primary body or you need reasonable AF.