Whatever the active ingredient in this product, there is no doubt that it is dissolved in acetone (nail polish remover).  Acetone smells bad and is HIGHLY flammable.  I would absolutely recommend against using this product inside your home or in an enclosed space.  Also, be aware that it says on the can that you should not smoke as you spray the product.
That said, I was very happy with the speed with which the first application dried (on my front step).  I was able to apply the second coat within a few minutes.  I sprayed a pair of boots and two pairs of walking shoes, all black, and there was no discoloration at all.
After the shoes had dried thoroughly, I tested the finish with drops of water, which beaded up and slipped off the leather with amazing speed. I am very pleased with the product.  But, again, I cannot emphasize strongly enough that this product should NOT be used indoors.

ADDED AFTER OUR RECORD 40-inch snowfall in February 2013.  This product is AMAZING.  I sprayed my boots in November and wore them regularly, since then, without respraying.  Then after the snow, I climbed over snowdrifts, struggled through thigh-high snow, stumbled into puddles and skidded through slush.  My feet never got wet.  This product does all it is supposed to do!!