Found at digg:
http://apcmag.com/apc/v3.nsf/0/E666E4A0A303D9AACA25712C008166C4
"Microsoft revealed today that it will not support EFI booting for Windows Vista on its launch. The news will be a shock for owners of Intel Macs who had hoped they would be able to dual-boot between Windows Vista and OS X. Intel Macs only support booting via EFI."
EFI support in Vista has been the thread of hope for those interested in a true dual-boot of Windows and OSX... that might not happen at all now, or at least not until the "subsequent release" of the client, whatever that means (Windows Vista SE? Service pack one? Patch?).
""A combination of factors changed our plans. The big one, in my opinion was platform availability. With this huge move to 64-bit based platforms and for us to support it, we needed to see a large heterogeneous sample of 64 bit implementations out there for us to feel comfortable in supporting it." said Ritz."
So... not a lot of PCs support it, which means Microsoft doesn't support it, which means there's no incentive for the hardware side to add EFI support.
If Microsoft just said "we're going to EFI for Vista, take it or leave it" - of course EFI would gain a lot of support very quickly, since Dell et al. will want to sell computers running the shiny new OS. And aren't the vast majority of Vista installs going to be on computers bought after its release? The number of people who will actually buy it in the store and upgrade on a PC they own right now has got to be fairly small (though maybe the margins are a lot better there).
It really seems like Microsoft's support for legacy systems is once again holding back the entire industry.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic