the phrase ‘doorway page’ has always confused me. as far as creating a page with perhaps a keyword stuffed paragraph on it with a button that says click here to enter the site. i’d never bother with doing that.
as far as creating a keyword rich page that is part of the site and may rank well for a word the index page is not designed to rank well for, i do that religiously. and i think that functions as a better ‘doorway’ to my site anyway.