Why? Allow me to explain.
An operating system isnt a stand-alone item. For an operating system to be successful it has to both thrive within and further foster the hardware and software ecosystem in which it lives. That means it has to not only provide a modern platform for hardware and software to come over the next few years, but it also has to provide a pretty broad base of support for existing hardware and software. And this is Vistas main Achilles Heel.
On a new PC with a relatively decent specification, Vista is a great operating system, demonstrating far better reliability and overall performance than XP (although gaming performance, to put it bluntly, still sucks whole lemons and this wont be improved until graphics card drivers reach a much greater level of maturity). The problems with Vista only really start to appear when you try to take a Vista PC and integrate it into an existing ecosystem of hardware and software. This is when you start seeing the ugly side of Vista.
There are two issues at play here. The first is that Windows Vista works very differently than previous versions of Windows, and these changes mean that the chances of software and drivers designed for XP working on Vista are significantly reduced. Some things will work, other things sort of work, and some things simply wont no matter how hard you try (or how much you rip your hair out, bang your head on the desk or throw expletives at the PC).
Secondly, there are a lot of vendors (both hardware and software) who have jumped on the release of Vista as a way to sell more hardware or updates software. While some companies have gone out of their way to offer support for Vista in the form of new drivers and updates for software, some havent (and probably wont) and this leaves consumers in the position of having to spend money on new hardware and software.
Back when Windows XP replaced Windows ME and Windows 2000, most home consumers upgraded all their hardware and software when they bought a new PC, and few had the savvy to try to move anything over to the new system. Now most home users are savvy enough to try to save a few bucks if they can. Also, more and more users (home users and small office/home office users) have more than one PC and are aware of more advanced PC features such as networking and file and printer sharing. Greater expectations make the probability of disappointment much greater.
Why werent more of these issues discovered during beta testing? The reason for this is that during the beta phase you cant really expect broad compatibility. The problem isnt that a new operating system makes stuff obsolete; the problem is that vendors dont address the issues. Most vendors didnt start getting serious about drivers and patches until Vista went RTM so there was little scope to test compatibility during the beta phase.
So there you have it. These are the reasons why I see Windows Vista as Titanic II. The Titanic wasnt sunk by any single build or design flaw, it was sunk by the environment in which it operated, and Vista is suffering much the same fate. The main difference between the two examples is that while the Titanic was sunk by a single iceberg, Vista doesnt have one glaring flaw, instead its being sunk by hundreds, if not thousands, of little tiny pinpricks resulting from hardware and software incompatibilities. The issues not only make life difficult for those who are already using Vista, but they are also having a dampening effect on those who are looking to make the switch soon.
Microsoft isnt helping matters either. It would be far easier for companies to plan for the future if they had an idea when to expect to see the first service pack release, but Microsoft is being very tight-lipped about any SP1 release date (probably fearing that announcing a date for Vista SP1 would stagnate sales in the interim). However, its important to bear in mind that this service pack is unlikely to improve hardware and software compatibility these were stuck with either way. But even with this in mind it would still be good to have some idea as to when we can expect to see Vista SP1 and what its likely to bring.
My belief is that the only real cure for Vista blues is to trash as much legacy hardware and software as possible. If you really want Vista, and want it to work properly, then the cost of that is likely to be far more than the cost of the upgrade.
If youre not willing to pay that price, its best to stick with your existing operating system.