Much simpler than it used to be, and it looks like I was right about Windows on ARM: it’s Metro-only.
Update: In the product matrix, Windows RT (the version for ARM-based notebooks and tablets) has the “Desktop”, but it does not have “Installation of x86/64 and desktop software”. So maybe it’s fairer to say I was half right. You’ve got “the desktop”, and built-in desktop apps like Windows Explorer and the Office suite, but you can’t install any third-party desktop apps.
So, it's not Metro only.
And you can install third-party desktop apps, just not ones compiled for x86/64. They need to be recompiled for ARM chipset.
Apart from that, spot on.