Right, just about 2 weeks from start to finish for us. You don't even necessarily need the Gong Zheng right away either, and the red marriage book you can get the same day. The only way I could see how it could take that long is because you have to go to the place where your spouse has his or her hukou to get it done.
We had friends whose marriage took forever because he was an Australian but his wife was from XJ, and they were living in Kunming, which made the trip a real hassle. They went back to XJ to get the marriage done, but were missing her temporary residence permit for Kunming which she needed because they had already filled in the form and listed her address as in KM (stupid thing to do, but once it was done they wouldn't let her change it) so they had to go back to Kunming and get it, then go back to XJ again. Of course between requesting time off of work and travel time and all, it was quite awhile before they finally got married.
If you bring everything you need the first time there's no reason it should take that long. We actually were missing something the first time we went to register too (the notarized translation of my passport) and had to come back the next week once we had that done, but luckily we were living in the city where my husband's hukou is registered to so it wasn't a big deal. Once we had all of our forms in order we were able to get married and get our book all in one day.
Maybe others can weigh in, I know lots of people here have gotten married in China.
(mods, maybe split this discussion to a new thread?)