I sure use em on my bent, more to keep my feet on the pedals which is more important in a bent position than an upright.
Thinking about though, I think it does increase my power a bit, the powerstroke being from about 10 to about 5. But maybe all it does is increase the inertia of my legs and reduce drag for the other leg, but even with only that as a helping factor think they help come end of the day.