I had one for many years before obtaining the Nikon 300/2.8 and the Tokina was a terrific lens. The focus was not as quick as the Nikon's, but in terms of color, contrast and sharpness, the Tokina was excellent.
If I recall, there are several versions of the Tokina, so be sure to get the most recent one.
By the way - the Tokina is built like a tank. when I was sampling the Tokina, the Tamron and the Sigma, there was no comparison; the Tokina is built way better and the image quality was the best of the 3.
No - the Tokina is not as sharp as the Nikon; NOTHING is as sharp as the Nikon 300/2.8, but it costs about 50% less than Nikon.
I had many many keepers shooting sideline sports with the Tokina.