I use that same one and have for around three years. A great product - does its job and is well made. I like that it is detachable too, so that I can bring it in when I'm worried it might get stolen and also easily take it off on days when it's not raining. I'd definitely recommend it.
Hey fluffhead...if it is slipping have you tried turning the little bolt on the side? It takes an allyn wrench and if you give it a few turns, tightens up the snap/bracket so that it shouldn't slip. Sorry if you already knew this, but thought I'd try and help you out if you didn't.