had my first passenger on the weekend there.
the bridge to the village was shut so i had to use the singletrack cutty to get the wife to the bus. Xtracycle beats walking.
It works well , wife was surprised at how well it copes with her on the back. Even climbing back to the house was easy.
It does most definantly benefit from the 36tooth front ring but now i find my self spinning out at 16mph on the flat.
Just picked up some dynamo lighting and a nexus front hub for it - all my other bikes run dynamos and the fit and forgetness is so worth while.