I took delivery of mine back in October, so I'm sure it was built before January. My MPG is lower than I'd like, but it has been getting consistently better and I only have 2700 miles on it. The break-in period is 6,000 miles. I also know my commute is really challenging for a hybrid (short - 7 miles, hilly and very cold for now).
In my unfortunate extra 20 miles driving on the highway, I did notice that if I stopped trying to hypermile, the C-Max was actually pretty good about mixing up the IC and Electric engine at highway speeds around 70 mph. I haven't spent any real time driving on the highway before. My current lifetime average is 33.7 MPG and this take is over 36.0 MPG. Far cry from the 47 MPG city/highway, but still better than my Camry Hybrid which dropped to 28 or less MPG in the Boston winter. I think the C-Max is more fun to drive too!