Speed Measurement Laboratories Inc. rated the blinder m20x @ 97% effective after 120 passes. I dunno how independent SML actually is, it may just be a setup for marketing.
http://www.usblinder.comfull report:
http://www.blinder.dk/sml.htmPrice: $300-$600
The consensus seems to be VEIL (Anti reflection coating) with blinder gives you almost complete protection.
http://www.laserveil.com/ Price: about $100-$150
this forum should give you hours of reading.
http://www.radardetector.net/