I can hear people saying, why another update so close to the major update of WordPress 3.5. Reason being, when there is major updates, to a script, as there was with 3.5, some bugs are found when the script is released to the general public. These might have slipped by in the beta version.
WordPress 3.5.1 fixes 37 bugs and some security issues. See the list here
I would suggest you update your script, immediately, especially as there is security issues. Please remember to backup your files and database.