I've pre-ordered an XO. Get it Friday with Forza.
What interests me, despite the fact the GPU in the PS4 is by all accounts superior. Is the fact that the XO SoC is supposed to be quite heavily customised.
It has 15 extra cores dedicated to other tasks, like audio for example. The actual CPU is supposed to also be customised, and the GPU is supposed to be heavily customised again - with hardware support for tile mapping or whatever it's called and custom hardware support built in for DX11.2 features.
How much horsesh*t that is I am not sure because I haven't seen Microsoft really push that story.