As Windows Vista reaches its first meaningful milestone--100 days of widespread availability, as measured from its January 29 consumer launch--it's time to begin analyzing whether the product is truly successful. Back in March, Microsoft announced that Vista sales were record setting, with more than 20 million Vista licenses sold in its first 30 days on the market, a rate double that of its predecessor, Windows XP. And in April, Microsoft credited better-than-expected Vista sales for the company's record quarterly revenue of $14.4 billion.

Still, Vista seems to have a shroud of controversy. Some high-profile technical bloggers have written about switching back to XP or even to a Macintosh, citing problems with Vista. There seems to be a lot of Vista hardware and software incompatibility horror stories on the Internet, with some suggesting that Vista be renamed Windows Me 2, after the ill-fated Windows release from 2000. And some bloggers have attempted to break down Microsoft's earnings in a dubious bid to prove that Vista isn't really selling as well as Microsoft claims.

So what's the truth? In the coming weeks, Microsoft will answer these and other questions as it addresses the 100 days milestone. We can also expect more information to come out at next week's Windows Hardware Engineering Conference (WinHEC). But for now, with the help of some numbers and statistics from Microsoft and other sources, I can shed some light on at least two measures of Vista's success.

First, let's look at Vista sales. In calendar year 2006, PC makers sold about 230 million PCs worldwide, and analysts expect PC sales to jump 8 to 11 percent this year. Assuming Vista is installed on most of those PCs--and it will be--you're going to see some pretty healthy numbers for Vista. (Microsoft has conservatively estimated a Vista installed base of 100 million by the end of 2007.) But in Microsoft's world, corporate sales are king. According to the company, corporate sales of Vista--despite all the rumors--are actually almost twice that of the previous record holder, Windows 2000.

But don't take Microsoft's word for it. Gartner claims that Vista will be installed on 4.2 percent of all business computers by the end of 2007, and IDC has estimated that number to be 5 percent. In comparison, Win2K was installed on 2.6 percent of all business computers after a year on the market. Note that these figures are based on percentages of the overall market: Vista isn't getting an artificial boost because the PC market is larger today. In addition, "InformationWeek" Research said that 25 percent of the 612 businesses it surveyed are currently deploying Vista, and an additional 17 percent plan to begin deploying Vista by the end of the year. That rate is also much higher than it was for previous Windows versions, according to "InformationWeek" Research.

Next, let's look at all the high-profile bloggers' problems with Vista. Although one might question the technical acuity of a so-called technical guru who can't handle a brand-new OS, you have to wonder if these critics have problems that translate into widespread, real-world problems. As it turns out, they don't. And this matches my own experiences: As a reviewer, I've installed Vista on numerous hardware configurations and have run into few compatibility problems. The problems I did have were quickly fixed right after Vista's consumer launch in January. So where are all these complaints coming from?

Obviously, some real compatibility problems do exist: Vista is a major Windows update with a completely redesigned driver model, a newly secured kernel, and a new graphics stack. Antivirus is an obvious area where Vista lagged behind at launch, although one might argue that antivirus vendors knew Vista was coming for years before it shipped. (Today, all five major antivirus vendors have Vista-compatible products on the market.) Overall, the very public noise about supposed compatibility problems has completely drowned out reality: Most devices (and applications, for that matter) work just fine with Vista.

Let's look at the numbers. In January, more than 1.5 million devices were Vista compatible. Today, there are 1.9 million Vista-compatible devices. Microsoft told me that number represents about 96 percent of the devices out there today. Sounds like a horrible level of compatibility, doesn't it? "We were more ready with ecosystem coverage--that is, application and device support--with Vista than we were with any other OS release," Windows Client Partner Platform Group Director Dave Wascha said. "This was a five-year effort aimed at getting our partners and customers ready."

In addition, Microsoft has added instrumentation to Vista so that customers can provide the company with feedback if something goes wrong. Thanks to this feedback, the company is making fixes at an unprecedented rate. More importantly, Microsoft is identifying the device driver incompatibilities that are causing the most problems and fixing those first. Of the remaining 4 percent of incompatible devices, or about 70,000 devices, 4,000 of them account for about 80 percent of the problems. "This is our bogey list right now," Wascha told me in a recent briefing. "So we're on the phone with vendors, flying out to meet with them, and getting these issues addressed. Once that's done, we'll do it all again."

So what's the criterion for getting a device to work in Vista? Wascha told me that Microsoft will fix or create drivers for any device that generates 500 or more user reports. "We have legions of engineers dedicated to this one purpose," Wascha said. "And we will continue to churn through that list." The only exception, of course, is drivers for devices that are no longer sold because the company that made them went out of business. "Unfortunately, the answer there is that it will never work," Wascha said.

Microsoft is caught in a catch-22 in some ways. Customers want the company to be innovative, but often don't like the side effects of that innovation. For example, Microsoft changed the graphics architecture in Vista to make it more visually exciting, but then some users complained that their video cards were no longer compatible. "Some people have had a less than stellar experiences with graphics cards," Wascha admitted. "This is a tiny minority of users. Unfortunately, it's been a vocal minority." Wascha wouldn't name the main culprit, but in my experience, NVIDIA's graphics cards have lagged behind ATI's, although the gap appears to have shrunk in recent days.

And what about those high-profile problems that the bloggers are grousing about? According to Wascha, those problems have never shown up in Vista's instrumentation. That's right: These bloggers actually opted out of Microsoft's feedback program. And when the fixed drivers do become available, you never see follow-up posts crediting Microsoft for fixing the problems. "We sit here and wrack our brains," Wascha said. "The drivers are out there."

Meanwhile, there are other pesky facts that just don't correlate with widespread opinion articles on the Internt. Microsoft is seeing one-third the number of security problems in Vista that it saw in XP's first 100 days. Application crashes are also being addressed more quickly. For example, Wascha noted that Microsoft shipped a compatibility fix for a bug that was causing applications to crash less than two days after the bug was reported. "We want to make sure that the perception out there about the product is accurate," Wascha said. "We're excited about the work we've done, and we know the system is working."