Apparently Canonical did something to X that prevents the Nvidia driver to rotate screens (via xrandr or the control panel GUI). This affects all Ubuntu based distros like Mint.To see if this might be the reason to switch to suse, debian, LMDE or arch, could someone on a non-ubuntu based distro confirm that rotating the screen actually works there (like suggested here)?
Can you rotate a screen with Nvidia drivers on a non-Ubuntu Linux?
nvidia;graphics;xrandr;display