Earlier today our friends at Neowin spotted that a preview of Windows Vista SP1 was made available through the MSDN Subscriber website, just to be removed hours later.
Although the final Service Pack is not expected until early 2008 this gives a good hint that Microsoft is making good advances on Vista SP1. While many are expecting SP1 to be a panacea, it's been reiterated that SP1 won't add any major functional changes in the OS, however a number of important bug fixes and performance improvements are to be expected, or so rumors indicate.
The fact is Vista is slowly acquiring the maturity many people expected at launch, although to be fair with Microsoft, it's near impossible to control such things as third party driver development and it's also hard to compare the scope of a new Windows release to say OS X, which is run on a very controlled environment. I probably belong to the minority of Vista users who have been running the OS since day 0 and have had little complaints on its overall stability and performance, but for the rest of the crowd SP1 will likely become the milestone they have been waiting for.