Another reason to be careful who gets webmaster tools access. A disgruntled ex-employee with access can do a lot of damage to a site. Re-target the site to a small island nation, or now remove key pages from the index.
When my site loses traffic, one of items on my checklist is now webmaster tools. Just to make sure nobody's fingers slipped on any of the controls. I haven't figured out ways to make sure QA monitors it. Its not as easy as "Make sure page X is crawlable, linked from the home page, and contains 'keyphrase' in the title".
I'd rather have these features than not, but I'm constantly frustrated by how "invisible" SEO problems are. robots.txt, meta tags, and webmaster tools don't affect how users see your site but they do affect how crawlers access and index your site. I've found that traffic loss due to problems in these areas is often harder to diagnose than more user visible problems.