Any question answered...

What is the benefit of Biopace chainrings? My new road bike has Shimano ones. I can't feel any difference to regular rings but then again this is my first geared/freewheel bike, so I don't have much to compare to.

There supposed to lessen the effects of the dead spot when the cranks are vertical by increasing the leverage through their ovalness as brother as already said. Sheldon Brown puts there demise down to Shimano's poor advertising saying they increased pedalling efficiency at lower cadences leaving people thinking they would be worse at higher cadences when this was not the case. I had it on one of my bikes which I gave to my bro in law and found it fine.