Aaah the mighty Bigma. Wish i got one when they were £750, now they are £1200! Instead I got a secondhand 170-500mm instead, which is not as good nor sharp. However it was only £300.
Now though, I would probably get the Pentax DA*300mm F4 instead, I know it is shorter, but with the 1.5 crop it does have an EFOV of 450mm on my Pentax's.