Laser guns are a "direct shot" which means the gun basically has to be aimed right at the radar detector in order for it to detect - basically it means that by the time the detector detects it, its too late, you've already been clocked.

Also, some cops will just pace you and get you that way - no radar involved.

I've gotten tickets from both of those before. I have a radar detector (a Cobra I got for cheap - I'm a Best Buy employee) and I don't find it to be that great of an investment - it picks up so much random crap...it beeps when I pass radio or cell phone antennas and certain stores and banks. Too many false alarms.

I personally can't justify spending 300+ dollars on a radar detector. I'd rather just pay the 100 dollar ticket and 30 bucks to take the class so my insurance isn't affected. Or just stop speeding. If you're that concerned, by a cheap one like I did and all the false alarms will make you paranoid into slowing down