Actually, they're nearly useless if you use software/OS capable of Emacs-style keyboard navigation and develop a habit of using C-a/C-e shortcuts. (Especially with CapsLock rebound as Control.)
I like them specifically for reading web pages. When reading I can just rest my hand on the right side of the keyboard and browse with home/pgup/pgdown/end. Usually when I'm reading like this I'm not typing and so not in the mood for ctrl gymnastics.
Actually, they're nearly useless if you use software/OS capable of Emacs-style keyboard navigation and develop a habit of using C-a/C-e shortcuts. (Especially with CapsLock rebound as Control.)