Was in NY last week and went to Prime Grill. First off, there's nowhere like it in the UK in so far as a smart kosher steakhouse that seems to be full all the time.
Being kosher for over 15yrs I've basically forgotten the taste of a good steak and these seemed very good to me. The steak I had on one occasion was excellently rare - although the sauce that came with it (something white with herbs) was far too salty. On a separate occasion I had the rib sandwich, again excellent, although the meat was closer to a stew than the ribs I know.
All in, an excellent experience