I have owned 8 radar detectors in the past, testing different ones out and such. I've tried Bel, Whistler and Cobra. I currently own a cobra and whistler, and I use the whistler. It's the mid range model with voice.
The only reason I'm not using my cobra is because it doesn't 'remember' settings. When I turn it off and back on, it is back to the defaults. The performance of the thing was great though. It cost me $40.
Trust me. I've tried up to $180 Bel detectors, and I can't tell that they work any better than the ones you can buy at wal-mart for $40. I've had the lowest model of both whistler and cobra, and I've tried the higher models too. The most important detection factor seems to be where you mount it in your car. I mount mine either up beside my rear view mirror, or right under my rear view mirror. Always mount it up high! You'll get better over-the-hill detection that way. Instructions always say "mount it just above the dash" but don't do that. That is only for laser detection, which doesn't matter anyway. If you get clocked by a laser, your detector will let you know right when it happens, not before, because it is intantaneous. I almost wonder why they even HAVE laser detection built in.
From my experience, more expensive isn't always better with detectors. Now I haven't tried the $300 up catagory. I've felt like I haven't needed to, personally. My cheap $40-$80 range detectors (all of them) have picked police up as far as a mile to a mile and a half away, especially on the open highway. I get about 2-3 seconds warning over hills in the country usually.
My .02.
