Well I have a bunch of it still stuck to my hands, but that's technically porous. Basically it sticks like a MFer. I had some spill out of holes under the car on to my epoxy garage floor. I was able to pry it off with a screwdriver, but what really happened was that I just tore the skin off the bottom of the foam mass. There's still a layer of foam stuck to the floor.

For adhesion, the surface just needs to be clean and oil-free. The MSDS for all of these foams include the phrase "removal: mechanical abrasion only" in them. That is, it ain't coming off.