Just did the move up to WordPress 2.5. New admin is slick.
Seemed to go smoothly except for some files upload errors on the new “Add media” controls. Quick search found others having the same issue.
Adding this line to my HTACCESS file got it working;
"SetEnvIfNoCase Request_URI ^/wp-admin/async-upload.php$ MODSEC_ENABLE=Off"
I’ll keep updating this as I find any issues or notes. Post comments if you see any weirdness.