I've only been once (today at lunch) but I think I have stumbled across a really good Chinese restaurant in Plano. Its name is 369 BBQ, located in the shopping center on the southwest corner of Legacy and Coit, hidden (somewhat) between an empty supermarket and the Hobby Lobby. It is hard to see from Legacy and impossible to see from Coit; you have to enter the shopping area to find it.
It appears to be new, and the servers are very helpful and friendly. Barbecued duck and pork hang behind a glass wall inside the entrance, but the food is much broader than barbecue. There's a very lengthy menu, with standards like lettuce wraps and mu shu pork, plus an extensive list of "chef's specials," which included Hong Kong style sweet and sour ribs -- sure to become a favorite of mine. Even more promising, the walls are covered with descriptions in Chinese characters of many dishes, which our server promised she would help lead us through if we came back.
Based on my one stop, I would say 369 BBQ has taken the lead over First Chinese BBQ as my favorite Chinese place in the area. I'll provide a more in-depth report at a later date, but this is good enough that I want to share the tip now.