I have recently used one of the new Sigma 150-500 lenses with my D300 to record a home match at my local rugby club.
The autofocus is rapid and almost silent.The optical stabilisation is brilliant. I was able shoot the whole match without needing a cumbersome monopod.
My only criticism is the rather stiff zoom ring. It is a minor irritation in view of the performance and incredible value for money.
I have enclosed one of my images which was taken with the lens.
Bromsgrove, Worcestershire, U.K.