Got the Tokina AF AT-X 300 PRO 300 mm F/2.8 yesterday and had a test this morning with the cat out the back on the fence.
Looking to use this for Golf/Sports photography and also Birds and Animals...etc I have a Kenko 1.4 Teleconverter which will make it a 420mm f4
It is quite heavy and will build my muscles. Sadly these can't be bought brand new any more, but I see it as a great entry point having a second hand lens as the equivalent Nikon or Canon would be worth thousands.
You can get one of these second hand for roughly $600-$1000 if your lucky. I was lucky as mine was owned by a professional photographer who only used it a few times, so It's like new