I'm a bit disappointed too for some of the above reasons listed - no IS, 82mm filter size and certainly the price is a disappointing surprise. That said, it looks like it will be a strong performer. The problem, I think, is that Canon DID listen to its customers and since people are stupid that was a mistake. What was one of the loudest complaints about the Mk I? "It's too heavy! I'm frail and can't lift anything for very long and it would never cross my mind to work out even just a little bit so I could hold a camera for more than a half hour without whining like an annoying weakling." Isn't that the biggest complaint everyone has with the fantastically performing 70-200 Mk II? So, they made The Brick smaller and lighter. Features add weight. Kinda sucks that we get less than we could have because of loud whiny weaklings.
The benefit for those of us with Mk Is that we're more or less happy with is that the new version doesn't necessarily pack enough of a punch to motivate immediate upgrade. We can sit back and use what we have while we wait and see how well the new boy performs. Even wait it out until a few are on the used market. I'm skeptical that the Tamron is gonna blow my mind enough to make that switch.
For the record I have no problem using a 7D with the 24-70 Mk I mounted for an extended period, the 70-200 Mk II gets a bit heavy after a couple hours of shooting but I've let myself get into "photographer shape" I guess.