From what I've seen of Windows 10, I'll be sticking to Windows 7, still. I mean, streaming from xbox to PC? That's stupid. That's undeniably stupid, and I don't know why you'd want to. Why not the other way around? If you're a gamer and you want some kind of one-way streaming, shouldn't it be obvious that you'd want to stream from the more powerful device? On top of that, your xbox is probably hooked up to a big TV, so you can stream from the more powerful device to a larger screen. But, instead, you stream from the less powerful device to a smaller device. I can see how it'd be good for recording and putting onto youtube, but I see now other reason for this.
In general, it seems like a few ideas all thrown together but not entirely thought through properly? Maybe that's just my perspective. It kind of seems like Windows 10 is a replacement for Games for Windows Live since that's now gone and dead. A lot of the things I saw at that most recent press conference looks like Microsoft's making a GFWL that emulates Steam but can also connect up to your xbox. I can kind of see why some people might like that, but, I, personally, wouldn't.