Agree with langer
I monitor hundreds of sitemaps with Google and there haven't been any issues with de-indexing any of the sites.
The XML format gives G a little more info about your site and the best parts of that is that it saves you some bandwidth (versus checking pages that never update...changefreq) and it helps them to focus on the pages you feel are most important (priority). It also lets them know which pages they need to come visit (lastmod) because their index is out of date for that page.
If you're running static PHP pages (real files for each page with some PHP thrown in), I have a script that will even allow you to support the If-Modified-Since and Last-Modified HTTP headers that Google likes so much. This script won't work if you have a smarty template, because all 'pages' come through 1 file, but it's worked wonders for me on a few sites.
-- This message may have been cut off and the rest will only be shown to members. To become a member, click here --