I wouldn't ditch my 16-35 for it. 35mm is too important for indoor stuff and 14mm is overkill at the wide end a lot of the time.
THOUGH I might buy one for ultra wide stuff if it was as good as the Nikon. I just would keep the 16-35 for event work as sometimes you need the 35mm end.
12-24 (usable on FF of course) would be awesome (again if the sharpness in the corners was up thar with the Nikon.
I for one am not one to say the 16-35 sucks as some are wont to do. I think it's an awesome lens. It can also easily use polarizers unlike the nikon, which makes it gooood. I have used the Nikon too. It's range in the long end is limiting of course, but you don't use that lens for the long end.
PICS OR IT DIDN'T HAPPEN:
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Although, Canon would have to make it 2.8 to keep it king of the UWA zooms. 

