Comments based on my experience
1) In the section on Forcing screen resolution, the second dtc command is wrong, it should be:
sudo dtc -I dts -O dtb -o devicetree.dtb devicetree.dts
i.e. the input file always comes last.
2) On my screen, a Samsung S22C360H, the lower resolution (1280x720) gave a poor picture: black was heavily textured, and many highlights had a sprinkling of incorrectly colored pixels. I reverted to 920x1080.
3) If you select a different resolution in xorg.conf, but do not specify the same resolution in the bootargs, the boot process becomes extremely slow, and switching from window manager to command line with crtl alt F2 never completes.
I hestitate to edit the article directly because I am a Linux newbie, and probably have the wrong end of several sticks! - compare the experience of [DrBeauWebber on the Parallella forum]