I just got back from a nostalgic re-run of my old commute (when I used to work in Dunfermline) on the latest demo from Laid Back Bikes...
Not only did I smash my previous record for getting to that office (averaging 18.5mph up from 17.9mph), I then turned about and rode the return leg at 17.5mph (previously would have been a strong second-best)!
The wheels are mine, but sub-20mph I'm not sure they offer much more than eye candy ;-)