I don't really understand why everyone is getting so worked up about this. I take it as meaning that MS is going to implement IE10 with as much low level integration to the OS as possible, i.e. it can make efficiencies by not having to support multiple platforms.

This is not the same thing as adding proprietary extensions to HTML5 that people seem to be inferring. Although IE9 doesn't support all of the HTML5 spec, so far as I've seen it hasn't added anything proprietary or invalid according to the spec, I don't see why they would change this for IE10