So, I received Tokina 11-16 f2.8 for the weekend from www.lensrentals.com. By the way, their service is great! Def. recommend.
Since I have only 7D+T2i (with crop sensor), not 5DmkII (with beautiful full sensor), I have to carefully choose the wide angle lesnes. I have owned Canon 24-70 f2.8 L, but never quite felt it was wide enough. So I bought really cheap EF-S lens (18-55 f3.5-5.6) lens just to see the difference. Quality-wise, it's a junk for video. For the photo, maybe it's OK, but for the video recording, I really dislike the quality, but again, it's cheap, what do you expect? Anyway, so I took quick snap shot of my editing room (that I spent about 20 hours per day), and compared side to side. Hope this helps.