I'd wondered what to make of the news that MS are to provide a futureproofing "strategy" for TNA by giving them copies of Virtual PC 2007, apart from it being a pragmatic step, and fortunately Chris Rusbridge has done the thinking for me. I guess I agree also that the progress with Open XML can only be good, since it's pretty much irrelevant that they aren't using the same standard as Open Office - the point it it's an open standard and XML is designed to be transfomed.
I'd be interested to know how TNA plan to integrate the emulation approach with any need they may have to preserve non-Windows or non-MS Office formats.