For a contrary perspective ... my knees need things to be "just right," and because of that, I do better with no float. It might take me a couple of tweaks when I get a new pair of shoes, to get the cleats aligned exactly right. But once I get it right, that's where my knees like to be, and float just means slop, to me. I can handle the 4.5° grey cleats that come with new Look pedals, but when I replace them, I get the black zero float cleats if the store has them.

+1 on talking to your fitter and your PT.