D800 rant after going into local store.

I do understand your desire to test the D800 before you spend the money, but I also understand the shop owners concerns.  If you put a few actuations on the camera, no problem if you go ahead a purchase the camera.  However, if you left without purchasing the camera the next patron would certainly request a discount because of the actuations on a new camera.  If the stores could afford demos for the various makes and models, that would be great.  However, most don't have enough spare money available.

Perhaps you know someone that would allow you to take a few shots with your lens and their D800.  Otherwise, you might take a look into renting one for a week to give it a good test.  Check out www.lensrentals.com.  They have the D800 available for $150 for 5 days plus $29 rt shipping.