I voted ergonomics and UI, because to me, ease of use falls into that category -- how much information do I get in the viewfinder? Do I have to go through a bunch of menus to change ISO?
I also give reviews a consideration, especially for things like autofocus systems. Unfortunately, price also has to play a big part for me, because I can't afford all of the camera I would like, but it isn't the No. 1 criteria for me. At least I was able to skip the D3000 and get the D3100 with my last purchase. Someday I'll upgrade my body, but I've got a couple more lenses and software to purchase before I'm ready for that.
I am always surprised some folks (10%) still consider megapixel as criteria #1.
That proves both marketing and camera-dumb sales guys pitch still have some effects
None of the above!
Final image quality is paramount!!
Ergonomics takes 2nd place.