Canvas is used many popular web applications but it hasn't gained widespread use because it isn't available in Internet Explorer. Despite this shortcoming, web developers have begun to find workarounds to allow equivalent functionality for IE users. Google had to develop ExCanvas to make their Maps available to IE users, for example. ExCanvas works around the limitations of IE by re-implementing much of Canvas' features using VML, Microsoft's proprietary version of SVG. Mozilla's plugin will make it unnecessary for future web developers to create their own libraries.
It appears that even if Microsoft can't or won't make Internet Explorer a modern web browser, the computer industry is finding workarounds.