Several analysts agreed that Microsoft has its work cut out for it, at least in the short term, because IE9 won't run on Windows XP, the aged-but-still-dominant operating system.
Microsoft omitted the still-popular XP from the supported OS list because, among other things, IE 9 speeds up page rendering and composition by tapping the graphics processor in newer PCs. Windows XP lacks support for the Direct2D API, which IE9 uses to accelerate content rendering.
The decision means that only a subset of machines will be able to run IE9, either in its preview or final form, until those systems and Windows XP are replaced by new hardware and Windows 7.
"That's an issue in terms of growth, at least for the next 12 to 18 months as more companies and consumers migrate to Windows 7," said Al Hilwa, an analyst with IDC. For that reason and others, Hilwa said not to expect a "tidal wave change in browser share. Microsoft's battle is not to lose much more share."
Worldwide, Windows XP PCs outnumber all other Windows-equipped machines by two to one, according to the most recent statistics from Web metrics company Net Applications.
In August, Windows XP powered 66.7% of the globe's Windows systems that went online in the month, while the three-year-old Vista accounted for 15.3% and 2009's Windows 7 for 17.4%.
Older versions of Windows, including Windows 2000, Windows 98 and Windows Millennium, made up the small remainder.
Even in the U.S., where Windows XP has a smaller slice of the Windows pie, the aging operating system remains in the majority. But its margin is much narrower. Here, Windows XP ran on 52.1% of all Windows PCs used to browse the Web last month, while Vista accounted for 27% and Windows 7 for 20.8%.
Windows' total share in the US. is significantly lower than its global share - 83.5% for the US, 91.3% worldwide - in part because Apple's Mac OS X is more popular in the United States than in most other countries. Net Applications, for example, pegged Mac OS X with a global share of 5% in August, but a U.S. share of 11.2%.
Other experts agreed with Hilwa that leaving out Windows XP is a problem for Microsoft's IE9 plans.
"This is a major shortcoming of the IE9 strategy," said Ray Valdes of Gartner in an interview Wednesday after the launch of the browser's beta. "And it's an opportunity for competitors to continue to chip away from IE's share."
Al Gillen, a colleague of Hilwa's at IDC seconded that. "The short term potential for IE9 is limited," Gillen said, noting that the new browser's numbers should pick up when Microsoft eventually offers it to Vista and Windows 7 users via Windows Update.
Microsoft has not set a final release for IE9, and Wednesday again declined to put a firm date on the final. Speculation has centered on an April 2011 release, which would coincide with MIX, the company's annual Web conference that's scheduled to run April 12-14, 2011, in Las Vegas.
"Firefox accelerates for Windows XP users too, something Microsoft says they can't do," said Aza Dotzler, Mozilla's lead technology evangelist, last week. "If Mozilla can accelerate browsing for the hundreds of millions of PC users on Microsoft's Windows XP, why can't Microsoft?"
Chrome will also feature partial hardware acceleration for Windows XP with version 7, which should be in users' hands in two months or less.
IE8, which debuted in March 2009 and currently has a 31.4% share, will be the most modern Microsoft browser available to Windows XP users through the operating system's support cut-off in April 2014.
Net Applications measures operating system usage share by mining data acquired from the 160 million unique visitors who browse the 40,000 Web sites it monitors for clients.