I hate citing Wikipedia articles but perhaps you should read these extracts.
"...Faced with ongoing delays and concerns about feature creep, Microsoft announced on August 27, 2004 that it had revised its plans. The original "Longhorn", based on the Windows XP source code, was scrapped, and Longhorn's development started anew, building on the Windows Server 2003 Service Pack 1 codebase, and re-incorporating only the features that would be intended for an actual operating system release.
Some previously announced features such as WinFS were dropped or postponed, and a new software development methodology called the "Security Development Lifecycle" was incorporated in an effort to address concerns with the security of the Windows codebase."
and
"...in conjunction with the fact that many of Microsoft's most skilled developers and engineers had been working on Windows Server 2003, led to the decision to "reset" development of Longhorn, building on the same code that would become Windows Server 2003 Service Pack 1, instead of the older Windows XP..."
Yes, you said Longhorn was scrapped, did you bother to even look at the link where Windows Server 2003 could be transformed into XP by simply performing about 10 easy to do steps ?
How to convert your Windows Server 2003... to a Workstation!
You actually have to use the XP cdrom to perform some of them as it copies and uses files from an XP installation to convert Server 2003. So now you are going to tell me that Server 2003 SP1 is the base for Longhorn. Does that really tell you all you need to know ? Longhorn was never scrapped as they put it. Just morphed from Server 2000 to Server 2003. Understand Server 2008 is based on Vista, but you tell me that's based upon Server 2003 and I've clearly delivered that indication that XP and 2003 are the same thing. Everything from enabling the cdrom burning, luna themes, Direct X, audio, System Restore features
"The most requested feature (apart from the Logon Screen & Fast User Switching) is here! You will need your Windows XP CD on hand to install this, as files from Windows XP are required to install System Restore into Windows Server 2003."
Windows Server 2003 is XP only in classic mode and by classic mode, it appears as Windows Server 2000 in it's gui and features.
What I find interesting, WinFS is not a feature of Vista, so it's NTFS again ? So what changed with regards to that (Vista) and XP ?
Anyway, this is beating a dead horse, you won't give up your argument in the debate and I hold my end just as vehemently. If Vista is a brand new OS for you, then it is and always will be. For me, I don't perceive it that way and never will.
I see it as I do Leopard, a lot of Tiger, less so from Panther and Jaguar. But OS X takes a lot from BSD Unix and Linux. Same holds with my view of Vista. It is XP/Server 2003 and that means that lurking around somewhere in Vista's revamped code is code from prior versions of Windows. You'd really have to compare the native processes that run for each, any new ones, you'd have to scrutinize to identify whether it was running as the base OS (out of necessity) or whether it was eye candy to be more or less superfluous and give you the impression of something you've never seen before.
Similarly Linux has Xorg for video, but the eye candy is Compiz. Well Vista has it's basic video and it's equivalent eye candy is Aero glass. They both have their own OS kernel, the heart of that in MS products is the NT kernel, and simply morphing it from version to version doesn't preclude the latest OS product as completely new, not even significantly different. Enhanced and feature rich maybe, but completely new, hardly. I even feel that way about the Linux kernel. Yes, comparing the 2008 kernels to the ones in the late 90's and the differences are going to be more pronounced, but the more recent kernels, subtle differences at best. MS and Apple run their kernels far longer than Linux distros.