If you haven't took the update, don't. It has a lot of issues. Some keep rebooting, Mine overheats and battery life drains quick. Have to charge 3 to 4 times a day
Did you do a factory reset after taking the update? Most of the users on our S4 sister forum have suggested this after the last two updates and its made a big difference with overall stability & performance. Give it a try and let us know how you make out. Good luck!