Originally Posted by Trakhak

The reason it disappeared:

When Biopace first appeared (on sport-touring bikes but not racing bikes), reviewers in bike magazines praised it to the skies.

Then Shimano got greedy and added Biopace to their racing bike component groups. Racers disliked the feel in general and when pedaling at high cadences and sprinting in particular and bad-mouthed it. The reviewers then did a 180 and damned it.

In response, Shimano introduced Biopace II, with much-reduced eccentricity (and some further, almost-round version whose name I've forgotten). But the damage was done, and Shimano soon gave up and dropped Biopace.

Ironically, Biopace made/makes perfect sense for the original target market.

The majority of casual and beginner sport cyclists (a.k.a. the majority of cyclists, period) have always tended to pedal a high-ish gear at a low cadence. Someone at Shimano noticed and figured that they could make cycling more enjoyable for those low-cadence cyclists by offering eccentric chainrings.

The idea was that, as a consequence of effectively reducing the gear ratio through the power section of the pedal stroke and increasing the ratio through the dead spots at the top and bottom, the rider's cadence would be higher and the load lower where it counted, with the bonus of more rest time per revolution.

A very few people have reported experiencing problems with Biopace over the years, many more have said that they've been happy with them, and the majority of users have probably been indifferent. Chances are therefore good that the OP will get along fine with them.