There’s an interesting research on .vimrc files in blog.venthur.de:
I downloaded 155 .vimrc files from the net (mostly from dotfiles.org and github.com), and wrote a little script which counts the number of times an option has been set.
The most popular option seems to be nocompatible, which doesn’t really do much at all. I guess the reason for the high rank is that plugin managers like Vundle ask the users to set the option before anything.
Understandably, tab-related options like tabstop, shiftwidth and autoindent rank high in the list. I was a bit shocked to find out that incsearch, which ranks number 3, doesn’t appear in my own .vimrc, but later realized that it had already been taken care of by vim-sensible đŸ˜€