Apple's line thus far is that aside from releasing its dual boot application, it will leave the Mac OS/Windows compatiblity issue to third parties. If this rumor is true, it represents a remarkable shift in priorites, from "yeah, we tossed Boot Camp together for the die hards, whatever" to "Vista compatiblity is so important we won't ship Leopard without it".
Frankly, I never bought Apple's disinterest in running Windows native. Steve Jobs is famous for expressing disinterest in a project while feverishly at work on it (e.g., iPhone, Intel Macs).
If this rumor is true, I would not at all be surprised to learn that Leopard runs all flavors of Windows native at full speed on the Mac OS desktop, with all of the Mac trimmings. This would explain why Apple has locked all developers out of the secret features loop: it will pee in a lot of cereal bowls! (And also why Jobs did not outline such features last autumn when Microsoft could still tweak code to lock the Mac OS out.)
Of course, Vista could just be a convenient excuse to cover a schedule slip on another front...
BTW, this would also explain Microsoft's decision to forbid using Vista in such a mode. They may have got wind of what is coming.
Remember the steps
of multi-tasking coming
to the Macintosh?
First Hertzfeld whipped up
Switcher. Then Apple built in
OS task switching . . .