Personally, I don't think it is worth the effort. Google Webmaster Tools are neat, but in my experience, a submission of a sitemap is not necessary. Same think probably applies to any other search engine that is worth being noticed (ie., the other two).
I suggest you focus on content and links, the rest will come with time.
I've not added a sitemap to my website, but the tools and the process of creating one has been useful in identifying any problems (broken/outdated links) and that's a good thing. Any good bot will find all your pages, and if it doesn't then it's not a very good bot! :)