Took the bike back in today. Turns out the screw for the "reach adjust feature" was not turned all the way. After the screw was all the way turned, it helped with the reach and now at least I'm able to shift to the big ring (however, still way more difficult than it should be). The mechanic said he has heard lots of dissatisfaction regarding the difficutly in shifting with 7900.

Note to Shimano: Your new "Reach Adjust" feature is a load of crap. There is absolutely no difference in reach from the prior 7800 shifters. The reason I bought 7900 was specifically for the "Reach Adjust" and now I wish I had stayed with my old 7800, or better yet, gone Campy. Live and learn.