I agree with you. I have the mark I and even if I have the money to buy the mark II, I wouldn't. The lens design of the mark I and including the 28-70 is much better than the mark II. Given that it is lighter and smaller it doesn't justify the new design as it is vulnerable in some situations. For example, from DigitalRev, Kai have mentioned and showed on youtube video that he dropped there company's 24-70 mark I and the only damage it has is the dent filter thread. Now imagine that happening to the new mark II lens. With its plastic filter thread, I cant imagine whats going to happen with that lens. Now I know that the chances of that happening is slim to none but if that happens, well, you better pray to the God of lenses.
On several occasions, one, when I was shooting a model on location, someone just pass by and bump in with my 24-70 mark I on it with the hood on. I was confident that nothing happened with the barrel because the hood protected the lens while I was shooting approximately at 35mm. On a separate occasion, I was walking around for a casual street photography, someone bump in again to my lens. And sure enough, I wasn't worried the lens was damage because the barrel was protected by the lens hood.
As I mentioned, even if I have the money to buy the mark II lens, I wouldn't, just simply because of the lens design. I just wish that the sharpness it has is also at the mark I version (based from users and reviews). However, when I was watching the review of SLRLounge on youtube comparing the mark I and mark II side-by-side, I can't see *any or *big difference against the mark I. Maybe because of the fact that I own the mark I and not the mark II that the ownership ego is getting the best of me to *blindly not admit the difference between the two versions. I would like to hear some comments regarding this issue after you watch the lens review from SLRLounge.