Out of the box, the resolution is set to 2160 x 1440 and the Desktop UI is scaled up to 150%. The Metro UI scales on it's own.
The only time you would want to change it is if you connect to an external display, like i have done here. I'm connected to a 24" monitor at 1920 x 1080 so i scaled the UI back to 100% since it's a bigger screen and lower resolution.
View attachment 2499
There are 2 minor problems with this:
1) every time you "dock" the laptop you have to manually adjust the scaling
2) changing the scaling requires a logoff/logon