For all of Microsoft's pushing of Vista, including boasts of incredible sales, reception of it has remained poor. Businesses around the world have been unwilling to upgrade, and after the initial waves the adoption rate for it has remained low. In the enterprise, despite being two years from launch, Vista is still found on less than 10% of business computers. That indicates that in the past 7 months, virtually nothing has changed.
This may play into Microsoft's favor, as they prepare to roll out Windows 7 at the end of this year or early 2010. Even if Vista's numbers continue to climb very slowly, it won't be long before a third option for businesses is available. It might also be encouragement for Microsoft to release Windows 7 ahead of schedule, though that is nothing more than speculation at this point. Of course, a rep from Microsoft claims that migrations to Vista are still in process, so before Windows 7 comes out we might actually see it break a 10% share.
The further we get from the Vista launch and closer to a Windows 7 launch, the more it seems that Vista may be skipped over by many. Regardless of any technological advantages it may have, the business world is a very important market for Microsoft, and Vista is doing poorly there.