From the same link, being able to take a full page screenshot (as in, below the fold) is also very excellent. I notice from the YouTube page description there is a further shortcut:
1. Open the Command Menu with Command+Shift+P (Mac) or Control+Shift+P (Windows, Linux, Chrome OS).
2. Start typing "Screenshots" and select "Capture full size screenshots".
I needed this literally yesterday, when I used MS Paint to cut and paste a screen together like a total mug.