Anybody use this lens.just now i found one for canon mount in beijing.the spec(especially constant 2.8f) is really appealing considering 250$ price,three year warranty.please share the experience

For video were you don't need auto focus it's not bad at all

For stills though, AF on the tokina lens is noisy and slow compare to other lenses in the class.

Sharpness should be fine for video use but again for stills it will show it's limitations.
For the money I would say it's worth to try it.

my purpose is video only...AF most probably i don't need ..i decided to give a shot

I use both this lens and the 80-200 for shooting video--they are a tad softer than the similar Canons but of course less expensive. Build quality is great, they are tanks. I like that both have clutches to allow for direct mechanical focusing. Color-wise they match my Zeiss ZE's better than the Canons. Good lenses.