Valentine... still the best if you drive highway. Don't waste your time with anything else if you drive highway. If you drive city, the next to the top of the line Bell is a great detector for the money, don't remember the model, but I believe it is V65 or something.
To defeat instant on radar, get a rabbit and follow the rabbit, staying well back. When he is lit up with instant on, your Valentine will squeal and you will know to slow down. Worse than instant on radar is LIDAR (laser). This is an infrared laser aimed at your vehicle. As soon as it hits your vehicle steady for 500 ms-- the officer has your speed. Valentine will pick up LIDAR, but you must use a rabbit to get reflected LIDAR bounced off his windshield before the officer paints yours. If he is painting yours, the Valentine is nothing more than a ticket notifier.
You can defeat LIDAR with LASER Jammers (which will also tell you your distance from an object infront of your vehicle, should you so desire). The legalities of using a laser jammer vary from state to state, just like radar detectors. Radar jammers are, of course, illegal anywhere in the US. The best LIDAR detectors are here, this is also a good site for detector info:
http://www.guysoflidar.com/july-2008/la ... -test.html
http://www.guysoflidar.com/laser-jammer ... ests1.html
Notice they test some on the Jeep Liberty, which is considered hard for a LIDAR jammer to work with because it is so big.