Thanks to everyone who replied to my question. I found your input to be very valuable and helpful.
I decided to go with the 70-200 f/4 IS, and placed my order for it and a 5D MK3 body today. While I love fast lenses, I went with the f/4 because compared to the f/2.8 II, it is $1000 less expensive after the current rebates are added in.
Equally important, and the real deal maker, is the size and weight of each. The f/2.8 II weighs 1490 grams and the f/4 comes in at 760 grams. I own the 24-70 f/2.8 which weights 950g. I actually like the heft of the 24-70, but it's on the edge of being uncomfortable to use hand held for more than an hour or so. I was afraid that the f/2.8 II would be too much to lug around, especially since travel photography is one of major uses I would put it to.