The problem is, pretty much everyone doesn't *want* a new OS
You got a 'new OS' in Vista, and you didn't like it. Leave aside the driver issues (generally solved for all but the most shit hardware), the file copying issues (fixed for most people after far too long) and the RAM requirements (cheap these days) Vista *is* a new version of Windows.
What are the real complaints about? Being slow? Due to not enough memory most of the time or really crappy graphics chipsets (we already know about Intel arm twisting Microsoft on that one).
Driver problems - you can argue about whether the architecture is better (it is in several areas, perhaps worse in others) but the manufacturers had a *very* long time to create drivers and simply didn't get off their arses. Perhaps you're thinking about the (annoying) loss of accelerated DirectSound? Well - like the Direct3D 10/10.1 support bitching by Nvidia, that's about having a consistent set of capabilities supported by *all* hardware. Which is what people want, instead of finding that something only properly works on an NVidia(or ATI) card, or only sounds ok on a Creative Labs card.
App compatibility - personally I've had very few apps fail. The ones that do fail generally do so because they're badly written and insist on admin privilege. Is it Vista's fault for attempting to enforce a configuration everyone should have been running XP/2000 in anyway? I will however grant that a) Microsoft's own apps were also sloppily written *cough*Visual Studio 2005*cough* and b) Whilst UAC isn't intrusive once you run decent apps, the Vista admin tools should not use UAC to view system settings, only to change them - shoddy move MS.
It was exactly the same with the 98/XP transition many people went through. Direct3D wasn't initially as fast, drivers didn't exist, *really* crappily written (ie. trying to write almost anywhere in memory) apps broke. Not to mention the interface whinges.
All most of the userbase is saying is that they really don't like change, which is one reason why Microsoft won't/can't make even bigger changes. They don't feel strongly enough about it to run OS X or non Apple Unixes either, otherwise you'd be buying Apple kit or a *nix box with some form of Windows virtulisation to run all your old apps. They can do that today, so this is all about not wanting to learn *any* new OS.
At some point the world does need to be dragged, kicking and screaming, into a more modern 64 bit, large memory and disk supporting, fully SATA capable, more secure and IPV6 capable by default OS. If not Vista, OS X, *BSD, Linux, Solaris etc. Otherwise things stagnate and x86 technology in particular has to carry on using horribly ancient hacks.