Best uses: de-greasing when your hair is icky, volume for when your hair is flat.
Why I love it: My hair is very fine and very flat a lot of the time. I also try not to wash it everyday. When it is dirty it really lays flat on my scalp and looks gross. This gives me a ton of volume and is fast and easy and it makes my hair not look oily anymore.
What I don't like: This does kinda turn my hair grey-ish. I'm sure if you have lighter colored hair it wouldn't be a problem. I have gotten really good at rubbing it in until it isn't noticeable.
How I use it: I spray it on my roots at the front of my hair back to my crown with my head upside down, (after shaking the can well) then I flip right side up and rub and rub and rub it into my roots. This gives a ton of volume as well as spreading out the product. Then I comb out my hair just a bit, starting lower down the hair shaft to not ruin the volume.