We run many WordPress instances and I've noticed some issues with at least 2 since the upgrade to 3.5. One of the main issues is the inability to type / access the editable fields in the Dashboard for Posts, Pages etc.
I've added the define('SCRIPT_DEBUG', true); to both wp-config.php files and some people said that alone fixed their problem but I did not get a fix at all.
On one of the other sites it seems to have de-activated or overridden the background slider we have on one of our themes.
Getting the Dashboard working is priority so we can make posts, edit pages etc.
I have viewed many other threads but none of the fixes for them seem to have fixed our problems and I saw that it was encouraged to post your own thread as everyone could have unique problems.