I get the feeling they didn't go with the HD, or the 8 mega pixel camera because they wanted the phone to be very distinguishable from the X. They didn't want the phone to be somewhat of the same thing as the X, with just a smaller screen.
When I picked the phone over the X, it was for a couple of different reasons. The first primarily being that the phone came with Android 2.2 already installed. I wasn't going to have to wait anymore for the latest operating system build. The second being it doesn't have the physical buttons on the front. I didn't want the physical buttons on the front that the X has.
Regarding the HD capability that is one of those things I'd probably never use. I'm not that interested in watching movies and such on my phone. I'll do that on the computer or tv. LOL
But, I do see your point. Ultimately the d2 is the same thing as the d1 only with a faster processor and some astetic changes.