I bought this brush a while ago, so I've been able to use it with my hair at various lengths and color conditions. Overall, it does exactly as it says: it smooths, reduces frizz, and reduces the dry time very nicely. However, if you have fine hair, it can eliminate any volume you were hoping to have with how smooth your hair comes out once dry.
I would use it on the bottom half to 2/3 of my hair when blow drying, using a different brush for the top where I really wanted volume to be. Using it that way absolutely helped cut down the drying time, leaving more time for styling.
The only big complaint I have is the handle of the brush. It's flat and very thin, making it hard to grasp well while blow drying. I've though of finding some sort of foam handle thing to put on it to make it easier to grip, but I've been lazy.