Interesting question. I am just preparing to post a 4th post in a series on SharePoint 2010, CSS3 and HTML5. The result was a little surprising. My examples were with the latest versions of Firefox and Chrome, and Internet explorer versions 8 - 10. No suprise that IE8 was a non-starter. IE9 performed rendering (other than CSS3 Gradients for which the DXImageTransform.Microsoft.gradient work-around was required) better than both competitors and IE10 from the Developer Preview outperformed everything. I'm hoping Microsoft adds CssGradients to IE10, but even if they don't they have certainly demonstrated a commitment to HTML5 and CSS3. While your rant and frustrations are understood and deserved, it's also good to give Miscrosoft credit when it responds to the user community requests. Look at this Modernizr compatibility array from IE10 - there's not much missing here. ;) no-flexboxr flexbox-legacyr canvasr canvastextr no-webglr no-touchr geolocationr postmessager no-websqldatabaser indexeddbr hashchanger historyr draganddropr websocketsr rgbar hslar multiplebgsr backgroundsizer no-borderimager borderradiusr boxshadowr textshadowr opacityr cssanimationsr csscolumnsr cssgradientsr no-cssreflectionsr csstransformsr csstransforms3dr csstransitionsr fontfacer generatedcontentr videor audior localstorager sessionstorager webworkersr applicationcacher svgr inlinesvgr no-smilr svgclippaths

If you're going to look back and laugh... you might as well laugh now.