I just don't think they're worth it. I have never ever ever gotten a ticket because I keep an eye out for cops, awareness is the best detector *disclaimer, don't speed, speeding is bad, I don't speed
Those things give off so many false alarms and then don't always detect the type of device being used by the cops.
Additionally, they'll also probably be widespread illegal within the next few years.
Anyways, enough lecturing, just make sure whatever you get is legal in your state