I, like Dale, am a professional in the industry with almost 40,000 bike unit sales since the 60's (and for the most part, basically one-on-one).
I am still selling Biopace rings on occassion with positive testimony by the users. I usually outfit the inner ring of triples and sometimes the center, but rarely the outer.
I think it was was one of the Stetinas that went 'inner only' alomg with other pros after the bios reached their peak.
I concluded that this arrangement allowed the derailleur cage to be uniformly close to the large chainring, allowing more accurate shifting. It also alowed 'round spinning' in the sprint and 'slow pounding' up the hills.
I remember the 'ring wars' in the old days In my ongoing research for my forthcoming book, there will be a couple of 'nothing's New' chapters. My old literature has examples of out-of-round- pedaling dating back near the early 1900's.
In the early 70's, Maruishi exhibited a bicycle at thje NY show with an elliptical ring. Roger Durham of Bullseye had hius E-wheel sometime in the early 70's, a very radical ellipse. We sold one of them a month ago to a guy who had one for 30 years
The Bullseye is for single-ring use only So then about the time of the Bio I started making jokes I called the Bio Wars Nobody actually seemed to agree on ther pattern
OvalTech by SR, Cycloid by Sugino, Bio then Bio 2 My joke was that Bio 3 would be round. So when they lost popularity, I stepped in and encouraged them for the inners and centers. After all, whatr's new isn't always what's best (another chapter in the book)
As far as habit, it is widely reported that after getting used to Bio, the round rings can seem odd.
Keep Spinning
Larry Black