I'm really only interested in seeing my website appear in the search results on Google. Why should I bother submitting my website anywhere else? Is there any benefit to a "global submissions" programme?
Given the volume of search traffic that Google accounts for, it's clear why the principle concern for all webmasters to have their website appear well on Google's search results pages. So much so, that other search engines and directories are rarely considered at all.
You should consider every search engine and directory as a marketing opportunity. Yet another place to broadcast your site to the world. All publicity is good publicity, as they say. You should also be aware that Google, and others, make an effort to track the level of traffic your website is receiving and from where that traffic originates. Therefore, the more websites, search engines, and directories that your website appears on, the better.
Your main concern should be in writing truly great copy for your website, in order to attract links from other websites and social sites. However, it makes sense to market your site as widely as your budget permits.