Yes, it does work! Surprised me! I can see where it would "waterproof" a fly, I don't spray it too heavily though. My technique is more of several quick sprays to form a mist. I've made a dozen or so casts before I reapply the spray.
For emergers, I cover the abdomen with my fingers, and spray the hackle. The hackle will float, and the abdomen hangs down in the water to mimic a real insect.
I agree that it also acts as an "attractant" to the fish.
And it sure is easy to use.