Plus, if it ain't broke, don't fix it. An OS being old is not justification to just release a new one. XP is not just old. As you pointed out, MM, XP has several service packs and has thus matured considerably. When Halo 2 came out for PC, it was claimed to only work in Windows Vista, but a few pirate hacks later, Halo 2 works flawlessly in XP. So, why do we need Vista again? It is clearly a Microsoft marketing ploy.
Here are my reasons for hating Vista.
First off, Microsoft goes overboard in treating the operating system like its Photoshop or something. It tries too hard to pack it with features, junk programs, pretty graphics, etc. Instead, Microsoft should be focusing on making a solid OS core that runs fast, has strong security, and manages memory effectively. It is abominable that Windows Vista requires a GIGABYTE of RAM to run smoothly. The same lousy excuse is always "get with the times; you need a fast computer". I agree with that relative to programs I need to run, not the bloody operating system. The OS should require very few resources to run. I should not need GIGs of RAM to play Solitaire comfortably. That is not "modern" design; that is lazy/stupid design.
Along these same lines, Microsoft is stupid for releasing 6+ versions of the cursed thing. Like I said, the OS should be simple and straightforward, not jam packed with garbage (or stripped of anything useful like that of Home Basic edition). Also, Microsoft makes stupid choices in which features it considers "premium". Aero, for example, is not that impressive... but oooooh, you can only get Aero if you buy Home Premium or higher! I have nothing against a company trying to make money, but Microsoft has lost touch with reality. It is no longer about delivering a product we really need; it is about maximizing profits by coercing people into thinking that Vista offers more than it really does.
Windows 95 had huge midnight release parties. Windows 95 was an answer to many people's prayers! It streamlined the UI and made the system much more useful. Many years later, Vista tries to come along and break the 7 year silence of XP... but with nothing more than a system that is memory-hungry, "secure", and packed with shiny graphics. Phailure.
XP does need an upgrade. There are many issues it needs to have addressed... but Vista was not that answer. Vista was a contract deal between Microsoft and Hollywood to ensure that HD content was locked down and "safe from piracy".