What's in your .vimrc file?
pyre: A good line to memorize:  :set et sts=4 sw=4 ts=4

  et  = expandtab (spaces instead of tabs)
  ts  = tabstop (the number of spaces that a tab equates to)
  sw  = shiftwidth (the number of spaces to use when indenting
        -- or de-indenting -- a line)
  sts = softtabstop (the number of spaces to use when expanding tabs)

Also you might want to move 'colorscheme twilight' into the ~/.gvimrc file instead; it makes the .vimrc file cleaner when you separated out all of the gui-specific stuff.My full vimrc and setup is here: http://github.com/bsandrow/vimc{edit}
Another good one:  noremap Y y$

By default Y is mapped to the equivalent of yy. This makes Y act like the 'copy/yank' equivalent of D.
{/edit}