I was curious to see what 550 feels like so I had a go. It was on an gym exercise bike, the fit sucks but I think the power numbers are fairly accurate. I had two go's at it after my swim, I hit 60s@550 both times. Its pretty intense and not all that impressive for me since thats only 5.5Watts/kg which is "untrained" according to some charts. Maybe with some practice I can do better.
Impressive work by the rest of you.