Also, NPD's U.S. commercial point-of-sale data, a database containing sales feeds from value added resellers, shows that 40 percent of Windows PCs sold to businesses now ship with Vista, while the other 60 percent still ship with XP. But that mirrors the pattern seen after the release of other new operating systems, he said.

"While the Vista percentage may seem low, it is very similar to the trend we saw after the XP launch. Businesses have historically taken their time with new operating system rollouts, and the trend we're seeing with Vista is very much in line with previous trends," Swenson said.

XP SP3 also contains numerous updates, including some important security upgrades, which were previously available individually, making it easier for IT departments to update machines. It also contains some functionality not available in previous stand alone updates, including Network Access Protection, a policy enforcement platform that enables XP SP3 users to take advantage of new features in Windows Server 2008.

 "NAP is an extremely important addition to XP, and will enable IT departments to enforce common policies throughout their PC fleet. But Microsoft's main messaging seems to be that, apart from NAP, there isn't much in the way of significant new features. I think that's a smart strategy, because if Microsoft included numerous new features into XP3, that would deter some people from rolling out Vista," he said.

Enderle also believes that, because of the critical mistakes Microsoft made with Vista, the market saw "a flawed, incomplete product, containing things they didn't want and nothing they did want, at an excessive price. It is no wonder IT said ‘no thanks.' Fixing that will be really tough." 

For his part, Cherry says that while Microsoft has acknowledged how important it is that releases be predictable and follow a road map or series of major and minor releases, it is equally important that Service Packs also be predictable, which is not currently the case.

But NPD's Swenson points out that while it would have been nice for Microsoft to space the release of XP SP3 and Vista SP1 out, SP3 had to wait until Windows Server 2008 was stable, so in many ways the company's hands were tied.