I've had every 70-200 Canon makes and had the 70-200 mk2 when I bought the 200, sold the 70-200 after a week when I promised myself I would keep it six months to be sure, but I have never looked back. There is NO lens like the 200 f2. It's simply insane in every aspect.
I bought mine used, it was hardly touched and only 13 months old and I saved 3238 dollars compared to buying it brand new. so it was actually only 2,5 times more than the 70-200 I already had..
The one lens I will NEVER sell..
Agree with Viggo, the 70-200f/2.8 II is a wonderful and very versatile Lens, the 200f/2 is simply a brilliant Lens.
If your thing is portraits I can't think of much that would do it better, the 200f/2 is a little less versatile than the 70-200f/2.8 II, but there's not much else that Canon make that's sharper then the 200f/2, maybe the 300f/2.8 II, maybe, I have all three, I generally grab the 200f/2 for anything other than wildlife..
I find myself more and more throwing the 200f/2 into the bag rather than the 70-200, unless I'm shooting wildlife, but for a longer Lens street work, Temples, People etc, the 200f/2 is just brilliant & it works so well on the 1Dx or the 5DMK III.
Be aware if you pick up a 2nd hand unit as Viggo has, you will need (unless it's been done) to get it into Canon to have the firmware upgraded for the 1Dx & 5DMK III, it works fine though without the upgrade on the earlier Canon Bodies, 5DMK II, 1DMK IV etc.