I had one for a few years in Nikon mount. It's a serviceable but not spectacular lens. It's extremely well built, and once stopped down to f/4 it's quite sharp across the field. It has the typical barrel distortion with a bit of mustache at 20mm and just a bit of pincushioning at 35mm. As is typical of Tokina lenses of the era, it's very well built mechanically, flares fairly easily, and has a subpar lens hood. The focus clutch mechanism is a bit awkward.
All told, it was a reasonable alternative to the Nikon 20-35mm f/2.8 at half the price. I eventually switched to a 17-35mm f/2.8 and only regretted it when it was time to replace the focus motor.