I may be in the minority but I have never been impressed with the Gristmill. It does have a nice atmosphere but the ridiculously long waits and mediocre food have always been a turn off for me.
My biggest gripe is that they don't have anything to offer vegetarians. I made the mistake of ordering their pasta dish once thinking that they finally added something to make the non-meat eaters happy. It sounded appetizing on the menu but when it arrived I realized that it was a cold pasta salad that is often served at backyard BBQs. Ok for a side dish but made a really bad meal! Maybe if they added more veggie choices I would change my opinion.