I bought this lens about 4 years ago. ITs sharp as a tack and works great. I have used the Nikons and I agree with the review below, which is worth reading. The Tokina 100 macro is as good as any of the Nikons of same focal length. If money is not an object, get the Nikon 200mm medical micro.
This lens is truly hard to beat for the money. I got mine used for $375.
Its hard to find a better website that
www.kenrockwell.com for solid information on anything Nikon or Canon including all the past lenses and bodies with tons of details as to what is good or bad about each item. Tons to learn for most amateur photographers for sure on all aspects of photography and equipment.
Quote: From Ken Rockwell
...The Tokina 100mm f/2.8 Macro is a fantastic lens.
It's optical performance is as good or better than the best from Nikon and Canon, and this Tokina's ergonomics, due to its unique focus clutch, is also better than any of Nikon's or Canon's 100mm or 105mm macro lenses.
All this, and this Tokina is less than half the price, just as well built, and smaller and lighter than any other 100mm or 105mm AF macro. Go get one!...
...The Nikon version 100mm f/2.8 AF works great with almost every film and digital Nikon camera made since 1977. You'll need to figure out a way to add a meter coupling prong for use with Nikons made from 1959-1976, if you want meter coupling.
The only incompatibility is that it will not autofocus with the cheapest D40, D40x, D60, D3000, D3100 or D5000, but if you focus manually, everything else works great. These cameras have in-finder focus confirmation dots to help you...
http://www.kenrockwell.com/tokina/100mm-f28.htm