I recently bought a new Nikon D300 body and this lens as part of a package. I was impressed by its build quality and the its performance in the first few images I took and I am happy to admit that paying a little more for a lens makes all the difference when one tries to get the best from a good camera.
One of the worries I had when choosing a lens was the build quality of Nikkor lenses of the same price bracket. I did not much like the look and feel of the new VR zooms, for instance. The Tokina is much better made and I am certain I do not regret buying a lens with internal focusing motors, when the focus is as quick and accurate with mine. The build quality is much appreciated - the one-touch manual focus switch and control is very useable and smooth. This is one lens I will not worry about when using it in poor weather, which is sometimes the case in the UK.
Also, having a fast lens can only help when composing shots and getting the best out of a digital camera. I like the brightness of the lens and the extra few stops it gives me in low-light conditions.
Overall, I am happy with my lens. One minor niggle is that the lens inhibits the internal flash, for fill-in work, due to its length and breadth. This is, however, mentioned in the lens's instructions.