I know this isn't helpful at all, but I had a moment today where I thought "Thank god I haven't switched pedals!" The drainage ditch from an overpass that goes over the bike trail got overwhelmed last night/this morning, so there were big rocks and mud EVERYWHERE. I ended up having carry my bike cross-style through it. I have SPDs, and I still had a hard time clipping in and out with all the mud on my shoes.

I do agree that the heat makes my foot discomfort worse. Does someone make well-ventilated mountain bike shoes?