This is one of my favourite Chinese restaurants in Calgary.
The atmosphere here is very casual and quite typical for a Chinese restaurant. The restaurant is spacious and can easily fit large groups of 8 to 10 people. The service here is pretty good relative to most Chinese restaurants - I've never had anyone slam a dish on the table here. There are an abundant amount of waitresses here, so service is pretty quick.
During prime meal hours this restaurant gets quite busy, so if you plan to go here for lunch it is probably best to show up a bit earlier. I am not sure if you can make reservations here, but I have never had to.
The food here is reasonably priced and the serving portions are huge; I always have a lot of trouble finishing the food I order here. Depending on the portion size that you get, the average prices range from under $10 and from $10 to $20.
I go here specifically when I am craving hot and sour soup. Most places that serve this dish tend to do a very sloppy job of it (either they make it to vinegary, or they don't have enough ingredients in it). Sun's does a phenomenal of making it; the flavour is perfect and there's an abundant amount of ingredients that they use (IE. mushrooms, BBQ meat, bamboo, etc.).
In addition to hot and sour soup, I like to get the "yin yang" dish. I am actually not sure what its called, but it is a seafood rice dish with half of the rice covered in a white cream sauce and the other half in a red tomato sauce. This and the soup are one of my favourite dishes and they are cooked quite well here.