I would suggest ND grads are must, assuming you will be using the lens for some landscape shots.
Having read many threads on the subject of vignetting with filters on this lens, I can now confirm the following to be my own experience -
With a hoya pro 1 protecter attached to the lens, and then a Cokin P wide holder on my Canon 10-22, vignetting is definitely there at 10mm. It just about disappears at 12mm.
I am unsure if the protecter (which is the slim version) was removed, if the vignetting would still be present. I do not intend to remove it to try as my own thoughts are that the protector is cheaper to replace, than the glass.
I may be wrong, but I would suspect any other makes of holders will have similar results, as the adpator rings are failry thin in the above combination.
Maybe someone that is brave enough to use this lens without a protecting filter, can confirm no vignetting at 10mm.