They are including XP because many business use very old legacy productivity applications that have not seen updates in years, and are incompatible with anything newer than XP
they're including XP because many enterprise users realized that Vista was junk and refused to "upgrade" to microsoft's new OS. microsoft is hoping to trick the enterprise user into believing that 7 is not Vista related, even though it's exactly what Saul said it was a few posts back- a rebranded Vista that now has the ability to appear like the OS they're used to using.
if i'm an enterprise user why do i need my productivity applications to be compatible with anything newer than XP? you do realize who's fault it is, if my productivity aps are not compatible with anything newer than XP, right? microsofts. MS chose to invent the need for a new OS.
they should have just continued NT's development through XP with their service pack crap & figure out a way to charge people for its development and continued support. instead, they're now launching Vista Part 2. i'm sure the new OS will launch will a lot fewer problems but the whole mess could have been avoided.
Vista, and now Windows 7 really make an admins life easier, in a perfect world. Most developers are making their apps Vista/W7 compatible now a days, but it is still tough for businesses to adopt the new standard. I think Vista/W7 offer features for admins and users that are valuable over what XP offers. XP is a solid OS but it's getting long in the tooth and relies on old technology, especially the x86 versions.
I don't think it's Microsofts fault for not provide support for legacy applications. Hell, we still run apps that are designed for 95 just because the new app would cost more to buy than supporting the old app does. I do like that we are getting thrown a bone here with the Windows XP mode, it will make migration alot easier.