cant beat 15mp in dx crop mode, I use mine in fx, 1.2x crop and 1.5(dx) crop mode all the time when doing wildlife, to get the "zoom" on prime lenses. just keeps me from dealing with large files and cropping anyways in post. 4fps, kinda sucks, but 5fps in 1.2crop and 1.5 crop modes. still I haven't had any problems with mine. it works great. you would be surprised at the resolution you can still get out of a 20+ year old 500mm f4 P lens on a 36mp d800. sharp at 100% when you get focus of coarse, cause its manual.