I have it too and definitely a must have for anything above 100 mm IMO. Especially if you use a polarizer.
That said, for fast moving objects, it's focusing speed is too slow and it will always be a fraction of a second late (car not perfectly sharp). Once you'll try an L lense all of a sudden this 70-300 feels VERY slow, but in isolation it's very good and IMO it should be heaps better than any Tamron, Sigma or Quantaray in the similar price range
__________________
|