Radar detectors are only illegal in Virginia and on military installations, unless you're driving a commercial vehicle. Waze is great, use it all the time, but it's only as good as the other users make it. I have a Beltronics RX-65 that I bought 6 years ago. It's old but it works; Ka detection is great. Only tickets I've had were when I was driving a different car and didn't have it, and the last one in my car was laser July 2015.
Some states will try to get you for having it in the windshield. I'm using a regular suction cup mount right behind my rearview because I'm too cheap to get a Blendmount. I have it hardwired (as well as my dash cams) into rear wiper power so it turns on with the ignition. Still, you cannot get a ticket specifically for having a radar detector unless you're in VA or you're driving a commercial truck over 10,000lb.