Google recently added new features to Sitemaps section in Webmaster Tools -- in addition to exisiting feedback, such as "how many Sitemap URLs have been indexed, or whether your Sitemaps have any errors." Also, the new Sitemaps page would replace the Video Sitemaps Labs feature, which will be retired.
In a January 26, blog post, a software engineer with webmaster tools revealed that with the new Sitemap "statistics from Web, Videos, Images and News are featured prominently. This lets you see how many items of each type were submitted (if any), and for some content types."
Also, Google now show how many items have been indexed.
Google says they have made improvements to the ability to test a Sitemap called "on-the-spot testing":
"Unlike an actual submission, testing does not submit your Sitemap to Google as it only checks it for errors. Testing requires a live fetch by Googlebot and usually takes a few seconds to complete. Note that the initial testing is not exhaustive and may not detect all issues; for example, errors that can only be identified once the URLs are downloaded are not be caught by the test," explains Kamila Primke, Software Engineer.
Also enhanced the way of displaying errors to better exposes what types of issues a Sitemap contains: -- Now, instead of "repeating the same kind of error many times for one Sitemap, errors and warnings are now grouped, and a few examples are given," said Primke.
Adding she said, "for Sitemap index files, we've aggregated errors and warnings from the child Sitemaps that the Sitemap index encloses. No longer will you need to click through each child Sitemap one by one."
Google also made changes the way the "Delete" button works. Now, "it removes the Sitemap from Webmaster Tools, both from your account and the accounts of the other owners of the site," revealed Primke.
Howerver, deleting Sitemap from Webmaster tools will not prevent Google or other search engines to read or process it, if you reference a Sitemap in your robots.txt file.
To truly prevent a Sitemap from being processed, remove the file from your server or block it via robots.txt.