Just updated from an old version of WordPress to 2.7
I have several pages that are for yearly updates, and have slugs that only have numbers (2006, 2007, etc.). These pages are the child of another page, and when trying to access them I would have to type the child's slug twice to access the page (e.g. /parent/2006/2006) Changing the slug to contain any other character solved the problem.
Another oddity I noticed it when using the Quick Edit for a Child Page, the em dash used to note that it is a child page disappears after you hit Save. It returns to normal when you refresh the page.