It's been 10 days since I upgraded to WordPress 2.0.  Right away, I noticed a problem and changed things around.  The problem is that you can't have a page with the same slug as the category base.  In other words, you can't have a page slug of "category" if "/category/" is your category base.  This wasn't an issue in WP 1.5, and I even retested it to make sure.  Another similar problem is that you can't have a page with a slug of "search" if you have the Search Rewrite plugin enabled (changing "?s=searchterm" to "/search/searchterm").  Maybe these things aren't problems.  Maybe they're "features".  Who knows.  Either way, it screwed things up and forced me to change things.