I copied the vimrc file I had set up at work to my local Linux machine (Ubuntu Gutsy Gibbon), expecting to get the same experience. I quickly noticed that I was unable to autoformat my Ruby files. When I typed 1G=G (or gg=G) to indent the whole file, everything shifted to the left and all indentation was lost.
I adjusted the vimrc to reflect some settings other Ruby hackers seemed to be enjoying:
behave mswin
syntax on
filetype plugin indent on
set nu
set showmatch
set ai
set et
set sw=2
set sts=2
set ts=8
set hls
colorscheme slate
set columns=140
set lines=35
set backup
set backupdir=~/.vim/backups
The line is bold is critical to my aim. I didn't have to set that anywhere under Windows for whatever reason. Once enabled, automatic indenting of many types of source code started working.