Koi Palace is the perfect, authentic dim sum experience. It's not as shi-shi as Yank Sing, but it's a nice atmosphere with truly outstanding food.
The ladies come by with carts of old favorites (BBQ pork buns, shrimp dumplings, custard tarts) and a bunch of delicious rarely-seen things (goose wrapped in a Uigher-style pancake, fried calamari that are dusted with something completely addictive).
Expect a wait -- this place is top quality. Your best bet is to line up right when they open or go at least an hour after they open (the first hour will be mobbed).
When you're waiting, be sure to stand inside, close to the announcer. If you're not right there when they call your number, they'll give away your table about 10 seconds later.