I think the other big question (apart from system specs), will be the backwards compatibility of add on aircraft and scenery. I make use of a lot of add ons that developers spend huge amounts of time on that I get to use for free but like a lot of folk I have also invested quite a lot of cash on on aircraft and scenery, particularly scenery that enhances where I live. It would be nice to know if I'll be able to "take it with me" to Microsoft Flight.