They're allowed to update the driver model; but as part of doing so, things are going to break, either by not having drivers, or by developers needing more time to develop drivers as good as "classic" ones. When this happens, it's not fair to lay blame entirely at the developer's feet; they didn't force the changes.
Yeah, Creative should probably have waited until their drivers were better quality before releasing. But if it's that or no drivers at all...?
They had plenty of time to update their drivers. It's not like as if Vista was a shocking surprise when it was released, Creative knew that MS had been working on it for five years. Beta 1 was released a full year and a half before Vista's launch, and Beta 2 was released 8 months in advance. They had plenty of time to get things in order so that their drivers were compatible with this new OS, but they just didn't try hard enough.
MS is by no means a perfect company, but it is not their fault that third parties released shoddy drivers for Vista.
Not only that, but Creative generally doesn't release more then a single driver a
year. There's no way you can cast that as MS's fault.
As a counterpoint, take nVidia. The initial Vista drivers were bad, had a lot of crashes, etc. What did they do? They kept working on them and releasing updated versions, including beta non-WHQL drivers until they got it right and in about 6 months the drivers were solid. There are
still issues with some Creative products and Vista. So, yes, changing the driver model can cause some initial shocks when the OS launches. That's expected. Having driver issues 2 years later? No.