Not much, but why would you switch to html5? There is limited support for actual html5 elements, and if your not using them, then your not using html5, just htm

Not much, but why would you switch to html5? There is limited support for actual html5 elements, and if your not using them, then your not using html5, just html4 loose. It's not like any browser is going to drop the html4 doctype so until there is widespread support for html5 elements (footer, article etc) there is no real benefit other than pr.