Do a search on the forums. Bit-tech misreported based on what all the other sites have. The spec sheet simply said "Anti-Aliasing" and numerous other sources had said 2xMSAA. In the interviews immediately following E3 (and at E3) with ATI and MS represenatives (see Anandtech, HardOCP, Extremetech, Firingsquad, etc) it was laid out that 2xMSAA as "free" but they really encouraged 4xMSAA because of the low overhead (1-5%; in retrospect the comment ""but it's not what you'd associate normally with 4x multisample AA" takes on a whole meaning of its own, i.e. "gotta design for it to get this sort of performance"). Anyhow, that link shows that you don't encourage developers to use 4xMSAA if it is required.
After some prodding in the immediate months after E3 it was made further clear that if a developer decided on DOF and Motion Blur, or other techniques that could minimize edge aliasing, that those too could be acceptible. Yet I believe a developer here noted that it you would be pushing your luck trying to get your app through validation without anti-aliasing of some sort.
That said, this seems to demonstrate the gap between the big heads at MS PR and the reality of their developer networking. Their biggest game in the first 12 months, Gears of War (well established at E3 2005 and reaffirmed at E3 2006) clearly was not going to have MSAA. MGS also went the route of not bankrolling "ground up" engines, but instead financed Mass Effect, Too Human, Lost Odessey, Crackdown, etc on UE3 which would not have MSAA. So the bulk of their initial 12 month offerings were using an engine that effectively would not support this bulletpoint.
Someone at MS had to know that many of the rendering techniques either in use (e.g. some games had no early z-pass) or the software in development (like UE3) were not going to work out, at least not at first. And that using a tiled framebuffer -- something not present on the PC side, where much of MS's support comes from -- could take a couple years to get proper support, and that in general multiplatform development could pose some hurdles. Obviously the marketing heads won. eDRAM is nice for a lot of reasons (even cost reduction), and games without MSAA benefit from it, but you sometimes wonder about MS PR. They leak like crazy, you have crazy people like the gal at E3 telling Epic to take out the chainsaw, and simple things like technical bulletpoints which in hindsight MS should have known would be a big issue.
