I have a pair of polarized lenses and I love, love, LOVE them! They block bounce-back glare, like the glare you get off of shiny chrome bumpers, windshields of approaching vehicles, and the reflection off of water (for this reason, they are awesome for fishermen. Polarized lenses enable the fishermen to see right down into the water.) Gray polarized lenses are the best for fishermen and multi-purpose use. I use mine for driving and they work excellent. Brown polarized lenses are great for golfers because it shows the texture on the green and on the fairway. Yellow polarized lenses are great for people who use gun ranges, as it makes the red bulls eye pop more.
As Hasafer above me posted, they can be expensive. I get mine with a backside anti-reflective coating on them to get rid of glare and reflection that comes from behind the wearer. I've also heard that pilots cannot wear them because they have a hard time seeing the digital instruments...I can't say for sure because I'm not a pilot, but I can tell you that if I tilt my head in my car while wearing them, I cannot see my digital clock as well. It has to do with the way the lenses are treated with the polarization. I forget at the moment why this is exactly...
