I havenever used them. I looked into the Shimano oval rings years ago, but never switched to them (they were pulled from the market).

While I haven't gone to oval chain rings, I have used my Computrainer virtual trainer and ergometer to analyze my pedal stroke. It measures applied power on my Trek for each 15 degree arc of the crank, and plots it in real time on the monitor, while you vary cadences and power levels. By watching the graphs, you get immediate feedback on your pedalling style, and can work to improve power output by ankling, etc. You build muscle memory (if that is the right term) so that your improved pedal motion carries over to road cycling. I understand that it is a training tool used by a lot of the Ironman competitors, to the point that they have put all the Ironman courses on their machine videos.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue