Shouldn't since the ergomo is optical and not strain measuring device.
I think EDR and RacerEx can give you non-bias reviews since they have both used multiple power meters. From what I have read the ergomo accuracy is very sensitive to proper installation. As far as the device measuring only one leg, well it really depends on what you are trying to achieve. If you want to directly measure your readings to your friend PT or SRM it may be off but if you are using it to log and train then it doesn't matter if you device read 100w high as long as it is consistent in that reading.
My only gripe with the ergomo is the ugly head unit.