I had a small selection of dim sum here for lunch on my trip to Hong Kong. I was by myself so I was given a table straight away... if you're in a group then I would imagine you do need to book ahead - especially for dinner.
The staff were friendly and very attentive. I think I drank my weight in Oolong tea. The dim sum I had was simple and filling. I had some steamed vegetarian dumplingin rice pastry, quite plain - I didn't get a dipping sauce to go with this one. The second dish was a spicy (but not too spicy) chicken dumpling in an egg pastry... steamed. These I highly recommend - I'm sorry I just can't remember the correct name.
Highly recommend a visit... especially if you can't get a table in the China Club.