It has often been remarked that IE is a headache for developers -- in part because Microsoft tends to prefer its own versions of web standards.
On the other hand, quite a few 'modern' web technologies -- including XHR -- were originally Microsoft innovations, only later adopted by..well, everyone else.
In some fundamental ways, IE9 actually handles what it handles extremely well -- Chakra, for example, and even the highly anti-IE 'nightmare for developers' post shows that IE9 uses less CPU time than Chrome, under Windows.
Of course, in terms of support for emerging web standards, IE9 is lagging well behind its competitors (cf. these charts). IE9 may do some things well, but it doesn't do as many things as other browsers do (even if it does some cool things, like pinned sites, that other browsers don't).
But Microsoft promises big changes for IE10, and just made available a new developer preview to prove it.
This new preview includes considerably expanded HTML5 support, and (most impressive to me) leverages hardware acceleration (ala Chakra) to speed up graphical technologies (e.g., SVG, CSS3 transforms) -- check out the embedded video in the full announcement.
Microsoft highlighted a few specific HTML5 features, newly available in this developer preview:
- Cross-Origin Resource Sharing (CORS) for safe use of XMLHttpRequest across domains.
- File API Writer support for blobBuilder allowing manipulation of large binary objects in script in the browser.
- CSS user-select property to control how end-users select elements in a Web page or application.
- Support for HTML5 video text captioning, including time-code, placement, and captioning file formats.