This ridiculous situation is basically stopping me buying films at the moment. I don't want to buy DVD's when there is HD available, I don't want to buy Blu Ray because I don't want to re-live the DVD experience and have boxes full of dusty discs, and I don't want to buy on iTunes in SD when it's surely only a matter of time before HD comes along - and from the 'iTunes Extras' experience, it looks like they're not going to allow upgrades from SD to HD movies, and I'm not prepared to buy twice.
I presume they're delaying HD downloads to encourage Blu Ray success. I just wish they knew that it wasn't going to work with me - I'll just not buy at all (at most I'll rent the HD version).