You get what you pay for..?

I have used this lens for a year now. I bought it because I could not afford a f/2.8 Canon lens and wanted something with that wide an aperture. After much study on the web and consulting other photographers I discovered this Sigma lens had roughly the same optical quality (slightly less) and speed of focus of the revered 70-200 Canon L lenses.

I purchased and took it too Italy for a field test.

Build quality is solid (Like a Tank)
Focus is fast and quiet and rarely hunts.
Has fulltime manual focus much like ring type USM on Canon lens
Is sharp and has great color.
Has never let me down in over a year

In short, I know you are supposed to get what you pay for but in this case I got much more!