Since my July post I've experimented with re-orienting the alloy road style Biopace 52/42 double. With the typical 5-bolt pattern we're limited to shifts of 72 degrees.
The 42T small Biopace didn't feel right in any orientation other than the original. It created dead spots that I didn't notice before. And I tried standard round 38 and 39 chainrings in place of the 42 but missed the Biopace. So it's back on the Trek 5900 in conventional orientation.
The 52T Biopace did feel better to me shifted 72 degrees clockwise, viewed from the drive side. It seemed to mesh better with my pedaling style. It's not as noticeable as the smaller 42T chainring which is more eccentric with noticeable elongation of the lobes. The larger 52 is only slightly eccentric, so it's pretty subtle.
And my Ironman still has conventional round chainrings. The only change I've made is to switch from the original Suntour plain 52/42 to Vuelta ramped and pinned 50T big ring and either 38 or 39 small ring -- depends on which freewheel I'm using and the anticipated terrain for a long ride. The Ironman is my easier effort bike, comfortable for longer rides and more casual group rides. I spin more, around 90-100 rpm. With the Biopace on the Trek I concentrate on lower cadence and more effort per stroke.
Still not a radical difference from round chainrings, but I'm tempted to try some real oval chainrings for another bike project I'm building up.