Just came back from Beijing with my new H1-B stamp. I waited for 7 weeks until the background check (Administrative Processing) was approved. It's now a routine for everyone working, studying, or attending conferences in the states. I heard most cases would take 2 months and some H1-B applicants had even waited for 6 months. So get prepared if you are going. You need the whole package for your first H1-B application, plus your resume, a detailed description of the work that you will be conducting when you come back, and an invitation letter from your employer.
Good luck!