Any question answered...

Ran biopace on my old bike before.

I can't says I notice the difference, much like the difference between 170mm and 175mm cranks, it's hard to feel the difference, except in your mind (and of course the toe overlap).

Some people claim to notice the difference, but as mdcc said, the placebo effect may have been a major contributing factor.

Used to think I was running 170mm, thought it was harder, turn out its actually 165mm, by then I no longer worried about crank length.

I definitely noticed going from my 175mm road cranks to the 165mm track cranks the other day- I road the 175's for ~600 miles constantly, then switched back to 165/fixed though.