Currently, I don't have a radar detector in my car (although I probably should!)  In the past, I've used a very basic Beltronics, which had a colored LED display and a simple escalating beep alert.  I believe it also detected laser signals. 

It always worked well, but would often pick up confusing "ghost" signals from supermarkets, etc, anything with moving doors I believe would set it off.

What are some features of "top-end" radar detectors that make them better than just a basic one?  Do they filter out these offending signals in a better way?  Are they more accurate?