The big one is less use of url rewriting. An important behind-the-scenes change.
When upgrading to beta 11, be sure to edit each of your apps, as the callback urls have changed. By editing the apps, the changes are synced to facebook.
Big changes to admin pages and the way app data is stored.
If upgrading from an earlier version, remember to run update.php as soon as you install this new code!
Then, go to each of your apps, click the edit tab and save changes. This will update the callback url on the facebook side.
Remember to keep the fb_devel.module enabled until you test your site and find no errors!
This should be the last beta with "big changes", before the 2.0 release.
Made significant fixes to user creation. This is a pretty big change so I tagged it.
Lots of minor fixes, too.
This is a beta in the sense that I don't plan to add new features before calling it an official release. The code needs some cleanup and probably more fixes before that release happens.