Quality is to be the overriding factor. Here's an interview with Jim Allchin:

http://www.techworld.com/security/ne...fm?NewsID=5263


"We want to make sure we drive the quality up very high," he said. "When we do something like Windows that’s literally going to [have] hundreds of millions of users using it, we want to build the highest-quality piece of software we can within a reasonable time frame. But at a certain point we make a determination: is this good enough for hundreds of millions or not? And if you rush something like that, then you end up harming everyone - our partners, us, our customers, so it has to be top of line."