GreenGranite,
Microsoft has just issued SP1 for Vista in beta form, to its testers. So it wont be long before it's shrinked wrapped. Also released in beta is SP3 for XP.
I would suggest a touch of caution here - many large organisations, and manufacturers, said that they would wait for the SP1 before they looked at rolling out Vista widely. This is mainly based on past experience that the SP1 tends to be a major upgrade to fix a load of the problems that got left in the original release.
In this case, I think Microsoft was a bit taken aback (certainly the Product Marketing guys I spoke to seemed to be genuinely shocked this time last year when they asked how many people would wait for SP1 & saw nearly all of the hands in the audience go up) so they have pushed forward an SP1 to get us all to move to Vista and I'm not sure that it has all of the content we'd like to see especially in regard to supporting legacy applications.
Of course we're now saying "We'll wait for a proper SP" but I guess it'll be like the first Vista release - we'll test it & make our own judgement based on how big an impact it will have on our support teams, SLAs etc.
That is the main reason why XP is going to SP3 - MS tried to can it earlier in the year & got a huge backlash against that, so SP3 is some of the features to help XP & Vista SP1 work better together.
Personally, I'm holding onto XP until I can see that Vista is as smooth & easy to use. And while I understand the comments about "Not Linux & not Mac", every Ubuntu Linux release gets smoother & easier and I figure the decision will soon get harder.