Just another thought on this.

If your left leg was doing 100w and your right leg 95 (i.e. 5% difference) your reported power would be 200w but actual would be 195w or 2.5% off. In other words, to say it only does half the job is a gross understatement of its usefulness. If there is a need to have really precise data, and no PM is perfect, then Stages may not be the best option, but if you only need good working/training data the left only is really not much of an issue. Of course, Stages does say the discrepancy is somewhat higher when doing things like a sprint but how often is that important.