Consider eclipse. It allows the user to configure every. Single. Thing. And in doing so makes configuration difficult because there are so many options. Sane defaults and a consistent environment are better, imho.
Those users who like the sane defaults can just stick with them. Those users who don't like those defaults can use the configuration options to fine-tune their experience.
IMO sane defaults and extremely detailed configuration go against each other. The detailed configuration makes it impossible to find the option you want.
Emacs is nothing like Eclipse. If anything, I would compare Eclipse to Vim: bare bone its useless, with plug-ins its just too big and unstable.
:)