ok I think there are some misconceptions here on what polarizing does. Polarized sunglasses reduce glare, what that means is for example when you look at water and you just see bright light, or the glare off a cars windshield, that kinda stuff. Somthin about horizontal light versus direct light or reflected light ect. I've seen polorized glasses with visable light transmision as high as 70someodd%, thats the number that counts on how dark its gonna be, you coudl prolly polorize clear lenses but i've never seen em.

Polorization won't make much of a differance mtnbiking, not too much glare, its really usefull out on the water. The only times it bad is when reading lcds and traveling on glaciers (can't see certain kinds of ice)

often people buy $200 sunglasses and go "wow polarzied glasses are really clear" its not the polarization, its the high optical quality of the lenses

go to the store try on the same pair of glasses in polarzied and nonpolarized (most stores will have oakleys in both with the same lenses) you prolly won't be able to tell the differance unless you are in a situation with glare (prolly not indoors)

Only reason not to get polarized is price (and thats a big reason)