Ive tried it a few times. I don't find it makes much of a difference, though it may be just the brand I used. I've used it so I wouldn't shampoo so often and also when my hair looked greasy and I needed to rush out of the house. I've heard it has worked well for others so I'm assuming it is just the brand I used.
I use it every now and then but I don't really like it because it does not take the greasy look fully away. Plus it leaves white specks all over that look like dandruff. It might be because it's a cheap drugstore brand but for now I do not like it. I will try a higher end brand though because dry shampoo is really convenient for those days when you are late and have no time to take a shower.