When I first arrived in China I was invited to a colleague's house to make jiaozi and ate so many that I couldn't face another one for around 8 years. That was until I stumbled into Baoyuan and now I've been going there 2-3 times a month. Service is brisk but helpful and the atmosphere is usually good as it is generally packed. Try to get there before 1215 for lunch to avoid waiting for a table. The dumplings themselves come in more varieties than you can shake a stick at. My favourite is the alliterative preserved pork, pepper and peanut which adds a bit of texture. They also do other dishes which have been above average given the relatively low cost. You can easily stuff four people and have a few beers for well under RMB150. I'd also recommend it for taking visitors from abroad as it has a "real China" feel but with the advantages of English menus and being pretty clean.

Good for kids too as you can ask them to do each variety in different coloured skins.