Many jump to the conclusion that Internet Explorer usage is directly linked with the market share of Microsoft Windows. The implication of that assumption being that IE6 is primarily still popular because Windows XP is still a dominant operating system. Capriotti explains, though, "While XP usage contributes to IE6 usage, the vast majority of commercial XP machines have already upgraded to IE7 or IE8. Less than 20% of web browsing on commercial XP machines comes from IE6."
One of the main reasons that organizations have been reluctant to upgrade from IE6 to IE8 is that they have nearly a decade of investment and development of custom business-critical applications that are designed to work with IE6. Migrating the browser requires also testing and updating those applications, which number in the thousands for some customers.
The reality of making the switch is not nearly as daunting as the apprehension would suggest, though. I spoke with Roger Capriotti and he told me that he hears regularly from customers that the process turned out to be much easier than had been anticipated, and that upgrading also provided an opportunity to inventory the apps that are out there and eliminate those that aren't even used any more.
There are two ways for IT admins to approach the browser upgrade. One is to put it off and just migrate by attrition when moving from Windows XP to Windows 7. IE8 is the default browser in Windows 7 already, so no additional effort would be required. For organizations planning to switch to Windows 7 in the near future, this might be the way to go.
However, switching everything at once--which might also include a hardware refresh--introduces a wide variety of variables simultaneously. If there are any issues with critical Web apps, troubleshooting will be more complicated. Organizations that are heavily invested in IE6 apps should consider upgrading the browser independently to focus specifically on the browser and minimize the number of moving parts involved.