I can't justify paying more than $100 dollars for a RADAR detector. This one does the job fine. All RADAR detectors will give false alarms for door openers, etc., since they use the same frequencies. Also, officers have to have their RADAR on for your detector to work. Some of the reviews on here whined about police officers being right next to them and it not going off.
For a cheap RADAR/LIDAR detector, the Cobras work just like they should. They cannot do magic, and neither can the $400 ones. The only advantage to the more expensive ones are if they come with remote mounted (front and rear) sensors. Otherwise, it's the same technology for 4x times the price.