Just to add my two cents to this thread, I have ALWAYS dry aged our Christmas Prime Rib and have had very good results in doing so. What I have done is placed the prime in a baking pan with a V-rack to catch any drippings. I have let it sit in the fridge for seven to ten days, uncovered. I then take it out shave any dry pieces off and then put the rub on and place it on the smoker. Ive also done this with steaks with good results.
Also Bobby Flay did a deal on his boy meets grill on 8/17/06 on prime rib and went to a New York butcher and picked up some dry aged rib eye and the butcher talked about the dry age process using slabs of dry aged beef that were up on top of the counter, it was interesting. From my experience it has always been a positive one with dry aging.