Oval chainrings (like Biopace, Rotor Q-Rings, etc.) are used by some pro cyclists. The oft-touted advantage for the system is the elimination of the "dead spot" at the top of the pedal stroke, but it still seems to very much be a case of personal preference. Just like there are some pros that prefer to spin an easier gear up a climb, while some would rather mash it out in the big ring.
It all comes down to how good the motor (legs+lungs) is.
It all comes down to how good the motor (legs+lungs) is.