In my experience, duplicate orders can be a significant issue (up to 5%). The hide submit module blocks them in a minimally intrusive way. When set into "hide button' mode it also helps users to know that the site is taking action as soon as they click the button - increasing user satisfaction. There are some bugs with admin forms that we should probably fix before this got included (#1957126: Make hide_submit compatible with views (disable within views?)) but other than that it works pretty well.