I upgraded yesterday and it works very well. Developers did a great work.
However I discovered a small issue. I saw some requests for some blog entries which aren't there yet (http://www.kubieziel.de/blog/index.php?p=222). WP answers that there is no entry which meets that criteria, but the HTTP status code is 200. IMHO it would be better to give a 404 back. Is there a way to achieve this or could that be build into the next versions?