I would love to here the inside story here. Based on my experience with Win7 and Win8, I expect that Win10 would have crawled (or not at all worked) with the slower CPU and smaller memory. My guess would be that the Raspberry Pi 2 is, in fact, a Microsoft initiative rather than an RPi Foundation initiative - and that Microsoft have actually contributed significant funds to make this possible. Either way, that is good…
Since it's ARM, you also won't see any of the "full programs" you see on x86 platforms. Just some simple mobile apps.
I don't think it's a "Microsoft initiative". Many RPi competitors have already moved to quad-core Cortex A7 chips, so it's quite predictable. But I'm actually quite disppointed by this move from the RPI Foundation. They should've skipped straight to Cortex A53. Now devs will have to support ARMv6, ARMv7 and a year or two from now ARMv8 as well.