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.