I dirty flashed from CM10.1 nightly and it worked perfectly fine, didn't need to restore apps or anything. The only problem was FC on Clock, but a simple clear data on Clock worked.
Not sure if it's my imagination, but 4.3 feels a lot faster than CM10.1. With CM10.1 I often need to pull up the apps list and clear them, otherwise loading slows down and things start lagging. Stock doesn't have to clear apps button, so at first I was swiping apps one by one to clear them, but I got lazy and left them as is, and I noticed didn't lag like it used to.