Stupid excuses, the only one I'd really buy at this point is that MS paid for exclusivity. Everything else sounds like horse shit to me.
In semi-related news, I saw a lot of absolutely massive displays hooked up to PCs at PAX this year. They were demoing nVidia's 3D glasses all over the place and one other technology, which I forget, but it had something like 6 LCDs hooked up to a single PC running a video game across all of them. We are talking about the equivalent of sitting 1 foot away from a damn omnitheater.