RMC33, the 200 f/2 is just a super lens, I only rented one for a few days.
Bdunbar79, I wasn't aware that the Mk2 has a lot of distortion. I thought it had almost none. In any case, if I needed a f/2.8 on a full frame, I would buy the Tamron over the Canon Mk2, or even try the old Sigma (if I didn't need sharpness or to make larger prints). Both the Tamron and the Canon M2 have "onion" bokeh, where the Canon Mk1 has very smooth bokeh. Not sure about the Sigma, although it supposedly has a lot of problems (and softness). If Sigma ever bring in a new one, it would probably kill them all. I would just wait on that one. I won't even own a FF till this Fall at the earliest.
Honestly if I was going to just blow a huge wad of money on a wide lens for a FF camera, I would probably buy several primes instead, like the Zeiss 15 f/2.8, etc. I already have the 50mm I want, so that leaves a 35...probably go with Sigma. I've rented the Canon 24mm f/1.4 Mk2 on my crop camera...didn't care much for it. It wasn't sharp at the edges until f/5.6. So that leaves the Zeiss 21mm f/2.8 Distagon, with its mustache distortion...it's supposedly still the best lens around this focal length.
And somebody needs to make a really good 28mm f/1.4, or dare I ask, an f/1.2. (Cosina) Voigtlander supposedly make a 35mm f/1.2 in Leica M mount...although seems like I've read it doesn't actually have the brightness of a 1.2.
Another Leica lens appeals to me, the 75mm f/2 Summicron. It's a shame the front half of a Canon camera has to be chopped off, in order to use M lenses...I guess Leica simply need to start making autofocus EF lenses...won't hold my breath.