no personal experienced, but plenty of professional athletes using them for good results what I have been told is that it takes to become used to pedalling with them as it changed your pedal stroke, and you need to fit them to all your bicycles otherwise your pedal stroke gets messed up if using a bike with round rings and also a bike with oval rings the O-Symetric chainrings are way more extreme than ones I have fitted before like Rotor

 You're right, these are more extreme. Before I only saw some more oval shaped rings. I've just checked - Shimano's Biopace have been made 30 years ago! wow

 Shimano f+died up bio pace - they got the rotation angle 90 degrees out and the rings were junk as a result.