Went back to Sweet n Tart Cafe (think that's the name) at 20 or 22 Mott...dim sum off menu at any time - not as much fun as trolleys - but ok. Also a smaller menu has really good dishes (not dim sum) something with chicken mushrooms and black beans was divine.
The service: One must beg for napkins, clean plates, etc. Could be more attentive. Couldn't have been less attentive when we were there.
sweet & tart, down the street a couple of blocks to the south has basically the same food as sweet & tart cafe, although I think the menu is broader? For real service and tableclothes sit upstairs and pay an extra dollar a person. Service is generally exemplary up there. For a hipper atmosphere, sit in the basement. For more blue collar dining at long tables, sit in the middle floor. All the same food, as best I can tell.