This place gets a very bad reputation, but I think undeservedly so. Admittedly the decor is a little tacky, it's open until very late, it's right underneath a nightculb that is the epitome of "sketchy", and is known for the enormous "scorpion bowl" cocktails they serve, but the food is much better than you'd think, and much better than you'd remember from five or seven years ago.
I had a late dinner there tonight (was really in the mood for Thai food, but at 10:30 PM all of the Thai restaurants that I could think of had already closed!) and was once again impressed by the food. Authentic Chinese it is not, but if you are embarassed to enjoy Americanized Chinese consider it "Fusion". Or a guilty pleasure.
I have had bad meals at the Hong Kong from time to time, but I think it really depends what you order. Tonight a friend and I had scallion pancakes, steamed chicken peking ravioli, chicken with basil leaves and some white rice. The scallion pancakes were cripsy and delightful --- not quite light, but not greasy either. They were served piping hot and had the perfect texture. The chicekn peking ravioli are best steamed, although I've had them pan-fried as well. These are large and very thick, which gives them a chewy texture, but a uniform one --- they are cooked through and through. They are filling because both the dough and the filling are provided in generous proportions. And the chicken with basil leaves is a nice entree that is at least "Thai-style." The chicken pieces are of good quality, and stir fried with various cut vegetables (mostly onions, green peppers, and celery), Thai basil leaves, and a slightly sweet but not overpowering brown sauce. The sauce and the basil make the dish mildly spicy.
The Hong Kong is not understated or subtle, but each of those dishes was very good. And the people are nice, the atmosphere kind of fun, and the hours can't be beat. I think it is the best Chinese restaurant in Harvard Square proper (it's only competition is the truly abysmal Yenching and the okay but unremarkable New Asia), although with Mulan, Mary Chung, and Zoe's a short distance away it's hard to choose the Hong Kong during normal hours unless you need takeout right away. But after 10 or 11 PM, I think it's even worth a trip.
Again, I have had some bad meals here in the past, but over the years I've found a number of dishes that I enjoy, and that I think they do very well. And they are extremely consistent. Here's my personal list of dishes that I think they do quite well:
Steamed Chicken Peking Ravioli
Roast Duck Soup with Lo Mein
Ginger, Scallion and Bean Sprouts over Pan Fried Noodles
Sweet and Sour Chicken
Yu Xiang Fish Fillet
Chicken Basil Leaves
Pinapple Fried Rice
Does anyone have other specific dishes to add?