It links for me, not sure what the problem is. If you go to the wattage group on Google groups and do a search on frame flex, you will find it. Common belief is it does affect sprinting, etc. but it really doesn't. It definitely "feels" faster, but it's simply not. I have found no technical analysis showing it does, and prof. Papadopoulos who helped write "Bicycling Science" agrees, as does Damon Rinard, engineer at Cervelo.

On page 367 of the third edition Bicycling Science, it says "There is
widespread conviction that a bicycle strength or stiffness enhances
either power production or propulsion. However, there is no
theoretical reason why this should be so, at least for stiffness
increases beyond the current level. Furthermore, we are aware of no
experimental demonstration to this point."