I fear that by the time they get Vista almost right it will be about the time they are Releasing the Vista replacement, much as what happened with XP. Here we are with a nature, relatively stable OS, which even with some of its faults can run on most systems and has drivers for most peripherals.
There is most certainly a lot of work to do on vista, even including some of the features that were slated for Vista like the new file system which got dropped, will it ever be included
The version after Vista is meant to being built from the ground up and no backwards compatibility with previous versions, something which has plagued many OS releases. Because of the no backwards compatibility MS though this would only take 18 months, I think not certainly if their time scales are anything like with previous releases (especially Vista).
If that were to happen in 18 months then I feel many would skip Vista completely and that is something I'm seriously considering as XP Pro will be supported for some time yet.