People forget that exactly the same thing happened with Windows 2000 and XP.
2000 was the first version of the new architecture (NT5.0) and when it was released nothing worked and it was ****** slow.
XP is NT5.1, basically Win2k with a new face, and by the time it was released, the compatibility issues were gone, everything had sped up nicely (partly because hardware had moved forwards and partly due to refinements).
Same story with Vista. Its NT6.0. You get the same compatibility issues etc all over again, "Windows 7" is infact NT6.1, so it is just Vista with a new face, and lots of refinements.
Unfortunately for Microsoft, Win2k wasnt aimed at home users, so the issues were never seen by the general public, and corporate machines were all generally standard enough not to cause issues, Vista however has been hit twofold, once becuase it was released to everyone at once, meaning everyone takes the compatibility hit and you get the correspondingly pathetic news reporting, and twice because the hardware manufacturers got in a huff with Microsofts minimum requirements, so MS reduced them to appease Intel etal, so you end up with Vista shipped on low end machines that really dont have enough RAM to run it properly, just so they could sell the hardware.