+1. I wasn't convinced, so I made myself some straps that served the same purpose, and I liked them. I suspect the PowerGrip ones are better than my DIY ones (which broke after a couple hundred miles).
The steel SPD cleat, clipped into the steel and aluminum pedal, screwed into the aluminum crank arm, with a whole steel bike frame at the other end of it, is an enormous heat sink. In warm weather that's not an issue, but on recent rides I've been getting really cold feet despite pretty good insulation.
Put on a heavier pair of wool socks, or shoe covers! problem solved. !!! DUH!!!