Folks, if anybody cares about RESULTS (rather than just on installing the plugin), let me tell you that SUBMITTING A SITEMAP CAN BE DEVASTATING FOR YOUR ESTABLISHED BLOG.
If you have a blog that has a lot of traffic, DO NOT SUBMIT A SITEMAP TO GOOGLE, because it will cut your Google referrals at least in half. Nobody knows why this is, (there’s plenty of discussion and conjecture about on Google Group Sitemap section) but I am just telling you what actually happens.
On the other hand, if your site is new, then installing the sitemap plugin and submitting sitemaps to Google seems to have a positive effect.
YOU ALL HAVE BEEN WARNED!