Interestingly enough, the USPSA equipment survey from the nationals just came out. For optics manufacturers in the Carry Optic division, it went like this:
Leupold = 36%
Sig = 29%
Vortex = 16%
C-More = 6%
Burris = 6%
Trijicon = 5%
Good info if you're setting up a competition gun.
Don't be confused into thinking that translates to a carry gun though; there are significant differences that shuffle those optic choices around a lot. 
