I saw over in Jill Wahlen’s forums where she saw that Google is treating index.html the same as the root domain now. While that’s good news, it should be a non-factor, as good webmastering begins with ensuring you have the proper redirects in place on your server so you don’t have to count on Google doing their job, you serve up what you want.

Seriously, don’t count on Google to do your job as webmaster, do it and do it right. If you want to read an article which covers this topic quite nicely, have a read:

Fixing Internal Duplicate Content