Some dude named Chris Froome uses asymetric chainrings. Seems to work for him when he's not crashing.

I have an old Biopace road double on my Trek 5900, the standard 130 bcd 52/42 set. I like the small ring effect on climbs. Seems to mesh with my less-than-smooth cadence. I tend to pedal squares when climbing. But I'd prefer a 38 or 39T small ring. I'd have to go to a 110 bcd crankset to get a ring smaller than 40 or so.

Can't tell any difference in the 52T, but that may be operator error.

The Biopace really aren't radically different from round, so don't expect a big difference. And it doesn't cause any shifting problems on my bike.

I prefer to spin around 90 rpm and the Biopace seems to thwart my natural cadence. So I'm trying to modify my style a bit on that bike and pedal around 60-80 rpm.

There's a theory that the Biopace rings should be re-oriented for some cyclists, depending on where their power stroke begins. I'm going to try that and see how it feels.

But as the newer makers of oval/asymetric chainrings usually say in their promotional material, they don't like to have their products compared with Biopace.