Mary Sue who? This Mary Sue: http://www.springhole.net/writing/whatisamarysue.htm
Do you find Mary Sue creeping into your stories and disrupting your plots? I could point out at least a couple of writers on SOL who have not only let Mary Sue into their stories, but have embraced her, eloped with her, and ran off to engage in carnal relations. :D
Some writers manage to make their MC a Mary Sue and still pull off a fun, entertaining story. I think they are the exception though.