I just noticed today that you can verify that you own a web site from within the google sitemaps website. The process is simple - Google will tell you to create a file on your site (something like /GOOGLEea6f95a80579477e.html), then they check to see if its there. If Google finds the file, your site is verified.

Why Verify?

When your site is verified google will show allow you to see any errors they encounter when crawling your site.

We will show you URLs that were either listed in your Sitemap or that we found through our regular crawl process that we were unable to crawl and we will provide information about why we couldn't crawl them. -Google

This is a great feature, but I am only experimenting with sitemaps right now. I am a bit cautious because I have heard about loss of traffic if you don't keep them up to date. Unfortunately you must submit a sitemap before you can get site statistics from Google.

Have you implemented sitemaps? Have you seen a positive or negative impact on traffic? Or no change at all?