It sounds like my experience was similar to other users' -- a meal at the Signature Room was a great way to enjoy to the view afforded by the Hancock Building. We went for lunch and scored a window seat on the dining room's east side. The buffet was good, though the minimal service we required was kind of lacking. Our waitress took our order, but only made it back to our table once to pick up some plates. All drink refills and even the check delivery was handled by a busboy. He was gracious, but it was a bit off-putting because it seemed our waitress couldn't be bothered. I think lunch and brunch accept casual diners, though dinner may be a bit more upscale. I have also heard that the Signature Lounge (96th floor) offers as good a view as the restaurant and the 94th floor observatory.
more