the 24-85 has a variable maximum aperture from 3.5 to 4.5 while the Tokina has a constant max aperture of 2.8 throughout the focal length range.
The range of focal length is different.
Filter size diameter is different (67mm for Nikon vs 77mm for Tokina, I think).
AF-S mechanism for Nikon, traditional screw-type AF mechanism for Tokina.
G lens for Nikon, meaning that it has limited functions on older Nikon bodies like F90X, F4. Full functions on newer Nikon bodies like F100, F80, D70, F5, F6, D1h, D1x. The Tokina should work on older and newer Nikon bodies.
Unfortunately I can't do a comparison on image quality here because I have not shot with the Tokina before, just briefly touched it in my hands. As for AF speed, can't really help you either ;p because I manual focus most of the time and all I can say is that for the opportunities I have missed on manual focus, I would have missed on AF and for those that I had grabbed on AF, I probably would have gotten them on manual anyway. But the saying that "what you pay is what you get" is generally true, if not in terms of image quality then in terms of build and handling...