I don't have any problem with this if they are able to deliver on the release date. I don't expect the game prior to the 15th, and I think that anyone else that does should lower this expectation. The release has always been the 15th, with early release at midnight through participating retailers and the digital download. What I do have an issue with, is the fact that I pre-ordered from Amazon in July 2010, a pre-order old enough for Amazon to be fully aware of, and it seems unlikely at this point that we'll be receiving the game on the day of release. That to me is very poor. Add to that the rumours that we're hearing that some Amazon orders have shipped, non-Prime and those that have had short pre-orders (again, could just be rumours but who knows) and that really seals the deal.
I've been an Amazon Prime customer for a few years now. I'd never threaten to cancel Prime because I think it is a fantastic service 95% of the time, but this issue over a longstanding pre-order is an absolute farce. Amazon knew that the game releases on May 15th, and they also knew that people wouldn't be able to play until it unlocks regardless of when they receive it. They're practically the biggest internet entertainment company, so why are they having stock issues? Surely they knew how big this release was going to be and would have adjusted their supplier orders accordingly?
I don't think I'll bother pre-ordering games from Amazon again. I stuck with my Amazon pre-order because it was £22.97. In future I'll just stump up the extra and go with Shopto.