IE9 team responds to Reddit questions: reddit tl;dr version
in response to a question about websockets and friends:Our approach when deciding what technologies to support starts with data. There are three things we consider: What are developers actually doing on the web today? What do developers want to do in the future? 
We started by building a tool to look at the top 7000 sites and what web APIs they used.Isn't this arse about? Isn't it kind of hard to use new tech if it isn't supported. I'd love to be able to use some of the new HTML5 things, but IE is holding us backXP is a platform that doesn't allow for the performance characteristics of a modern web experience.WTF sort of a response is that? There's some good answers in there, but this sort of spin-driven markety rhubarb works so hard to hide it. Why not just say that IE9 makes use of features available in Vista and 7, but not in XP.