CBs are good on the interstate, but so little of my driving is done on a road that is likely to have a CBer ahead of me as to make a CB useless for "situational awareness"
Instant on is really 2 pulses. The instant on pulse tells the officer you are going fast enough to warrant another pulse. The second pulse is all that's admissable in court. My V1 keeps me from getting the second pulse, well keeps me from getting the second pulse at the original speed.
With so many cities up-ing their revenue streams by increased traffic enforcement due to the bad economy you can't afford not to have a radar detector. And then there are the cities that have always been heavy on the enforcement side with rolling radar, constantly changing speed limits, short yellows, etc., etc.
A radar detector also warns you of impending traffic issues. Emergency vehicles and road work typically now have a transmitter
Buy the cheapest damned one you can. Mine has saved my ass more times than I can count. If you get hit with Laser, the mighty V1 is going to do the same thing as the $20 wally world one. Plus, mine tells me to "fasten my seatbelt" when I start the car. Take THAT $400 piece of crap! 
. Although I never used radar, my recommendation is to contest the citation:
