The major problem is testing. Many corporations have in-house Web applications—both custom and third-party—that they access through their Web browsers, and before any new browser upgrade can be deployed to users, it must be tested to verify that it works correctly and doesn’t cause any trouble with business-critical applications. With Mozilla’s new policy, this kind of testing and validation is essentially impossible: version 5 may contain critical security fixes not found in version 4, and with version 4 end-of-lifed, the only way to deploy those fixes is to upgrade to version 5. (c)
Rephrasing this paragraph, I’d say: “Stop developing for IE6 and get yourself a life..”
