I found the following link in this forum (CR):
(Credit to the original uploader) that mentions autofocus problems of the Tokina with the 7D (especially the non center point)
In that article you can find also a reference to:
This backs my distrust in 3rd party lens makers.
Of course they may solve it but again what happens with the future EOS bodies?
Thanks for the links! I can happily rule out the Tokina since so many people are having issues with that lens and the 7D, I don't use autofocus very often (especially with wide angle landscape work) but obviously it's worthwhile to have a lens that works 100% with your camera, especially when you're spending decent amounts of money on them!