I have both a Shakedry jacket and Shakedry cap. I've gotten the jacket to have a thin layer of moisture on the inside, never more. Bought the cap recently and first wore it on my commute when the forecast called for rain that never fell. When I took it off, it was absolutely dry. When I've worn fabric caps (polyester, never cotton) they have been completely soaked from sweat at the end of the same commute.
The downside of the Shakedry tech is that it isn't reinforced for wear and tear, so high friction contact points are not good applications for it. That and it can be very expensive if you don't find it on sale -- when it is on sale, it's only somewhat expensive.