I type 110 WPM and have been trying out the 12" Macbook for the past couple weeks. I could never get along with it in the store (mistakes galore), but after a few days of use I put up near 100 WPM numbers with minimal mistakes. You do adjust -- my finger touch has gotten lighter, and as a programmer my quick typing bursts actually do feel quicker due to the less amount of movement/pressure needed.
That said, I just don't find it particularly enjoyable. Going back to my 13" rMBP is just a flat-out more satisfying experience.