This lens produced some very nice shots when it worked.
Right out of the box it gave me an err 99 on a 20d, I powered down and reinstalled it, that seemed to do the trick for a little while, but err 99 kept coming back. Did everything i could, new battery, powered down. reinstalled lens cleaned contacts. reset firmware. upgraded firmware.
Finally called tokina they told me they were not aware of the problem but sounded like stuck diaphram, they recommended me shipping it to them for service. Yeah right, a brand new lens, service, no thanks.
Finally sent it back after 1 week of frustration, back for a new copy this one lasted a whole 4 hours and completely froze aperture it was stuck around f8 and i could see the blades were cock-eyed. I though maybe just this model. NO luck with th 28-80 either.
AF had troubles indoors low light, seeking.
Again I did get some very sharp shots, with it's slow AF
and the MF was very smooth.
Aside from that i was impressed by the external build.