Those are the do it all swiss-army-knife of bikes, I think. I figured it would give up a lot 'on road', but I was extremely impressed with iDave's (from ADV) ability to ride the wheels off his and run about as quick a pace as I'm comfortable riding on the street on a supersport.
Here's my buddy Brent chasing Dave on an 05~06 Wee - 2up with clapped-out 50k stock suspension (hard to see with the extreme fish-eye of the GoPro).
http://www.youtube.com/watch?v=rdpqN8w65Hc
One thing I'd highly recommend - cartridge emulators & an upgraded shock, since it's a pogo-stick in stock form (but obviously that doesn't keep a skilled rider from flogging the snot out of one

)