Re: Games, anyone?
Valve's not going to charge Windows 10 S users anything, because Steam's not on the Windows app store and probably will never be, since it's a direct competitor to Microsoft's store. Instead, Windows users will switch out of S mode. And if S mode becomes the default on new installs or even better, if Microsoft wants to charge money to switch people out of it, EU anti-trust is going to come down like several tons of bricks.
Building Steam for ARM's probably not too difficult, but how much work is it going to be to convert games to ARM? Win32/64 to Linux isn't generally too hard, especially if it's something you've considered from the start, but from there to ARM is quite a leap.