Just a note that "dim sum" is the name for the dishes, and only in the U.S. does it refer to the style of eating. Everywhere else, including the U.K., Australia, and Hong Kong itself, it is called "yum cha", which means "to drink tea". You would never say "let's go have dim sum" in HK, you would say "let's go yum cha."
It's my dream to go to Hong Kong (I am British), turns out all the reading I do on the city has actually stuck in my head, did better than I thought I would! 18/20 :)
I'd say Cantonese is a language in its own right, not a dialect, specially considering that with Mandarin are mutually unitelligible, have different grammar, etc.
+1; Cantonese is too mutually unintelligible to be considered the same language with Mandarin. It should be considered under the language branch Yue (Cantonese).
Just gonna share (irrelevant), Jackie Chan is only loved by people from the western world. In Hong Kong, he is one of the most hated people because of his misbehaviours and also inappropriate speeches.
Dim Sum is more of a dish than a 'style'. While there are many different kinds of Dim Sum I don't think it can be classified as a style. Pretty sure most of the people who got that wrong got confused by this terminology.