Let me ask the group...I own a 70-200 f/2.8 IS Mk II. Would I see enough of a difference with the 135 @f/2 to make it worth buying a nice used one?
6D, Fuji X-T1, X-E1
Tamron 24-70 2.8 VC, 70-200 f/2.8L IS II, 400mm f/2.8L II, 100mm L IS Macro, Sigma 85mm, & 35mm f/1.4's, Rokinon 14mm f/2.8,
Fuji 23mm 1.4, 35mm 1.4, 56mm 1.2, 14mm 2.8, 18-55, 55-200