My father in law is a hardcore clip user... he tells me he can 'toe and heal' with them? I am assuming this mean that in addition to pushing down on one pedal... he also uses the other foot to lift the other pedal, which I suppose means he is getting twice as much drive for his energy?

This is why I find the Powergrips interesting, I am not keen on having to actually ,ess abput and snap my foot on to a pedal, but I would give the Powergrips a try.