I haven't used it in production, just played around with it. Initial impression is that it works as advertised -- it sticks to tips and best practices that are widely accepted as correct for all search engines, and its good at catching little mistakes that otherwise would have gone undetected.
There is more to the IIS SEO toolkit than just site analysis, there is also something about robots.txt and sitemaps. I haven't looked at these yet.
Just for SEO alone the IIS SEO Toolkit should IMHO be well worth your time.
Check this out from SEOMoz : http://www.seomoz.org/blog/the-web-developers-seo-cheat-sheet, and the tips from Gabriel Weinberg http://www.gabrielweinberg.com/blog/2009/04/search-engine-optimization-seo-tips.html. After this, you have PLENTY of stuff to work with. My $.02