I experimented with this stuff toward the end of last season when my autocover died. The pool was going to be demoed in another month or so anyway, so I didn't bother to get it fixed. I figured what the heck, let's see what this 'solar-cover-in-a-can' is all about.
The way it works is that it creates a molecular layer on the water surface. It's totally invisible and you can't tell it's in the water when swimming. It didn't seem to affect my filter or water chemistry much at all. The product I used needed to be added about once a week.
While it's all great in theory, it falls way short in actual practice. The only points I'd give it is, that provided your water is very still, and there is no breeze, it will cut down on evaporation better than if you were using absolutely nothing at all. Under ideal conditions, it may be about a 1/4 to 1/3 as effective as a bubble solar cover. If the water is disturbed at all, even if a breeze is blowing across the water, the molecular layer will 'bunch up' and create holes in the coverage, thereby rendering it useless. It takes a while for the layer to reorganize itself across the water, and again, will only do so if the surface is perfectly still.
So for me, the results of using it were so minimal that it wasn't worth it.