The Hang Ah Tearoom, tucked into an alley off Sacramento Street, was my introduction to dim sum, Circa 1960. As far as I know, it was the first and only dim sum place in SF at the time, predating Yank Sing by quite a bit.
The place had a marvelously funky Old Chinatown ambience to it, like something out of a paperback novel or a B movie. If there's a watchdog organization for the preservation of local ambience, this place should be on their protected list.
They wheeled around carts containing the little plates of goodies for us non-Chinese speakers to point and pick. Wonderful stuff, made even more so because it was so unfamiliar and exotic at the time.
I am glad to see, according to whitepages.com, that it still exists - although there was no mention of it in yellowpages.com or zagat.com. They must keep a low profile.
I haven't been there in years. Is it still worthwhile?