i'll try not to rant too hard but Kies and OTA firmware updates are a joke. you are essentially dirty flashing one rom over another with no real clearing of caches, no resetting, no way for all the programs to regroup, rebuild and run on the system hardware/software properly. the thing about dirty flashing is, it sticks well with some devices but generally not with many others. you'll see these types of issues many times among the avid flashers and those that must have the latest release of a developers rom.
i would recommend backing everything up, booting into stock recovery, wiping data/factory reset and wiping cache. if you decide to perform another update via kies in the future, i would do this procedure before AND after the update.
yes, you have to start over when you perform these sorts of actions but you have to ask yourself, are you happy with how your device is performing now (before the update)? is it worth starting over? (it might be if you're going to run on the updated OS for a year or so) and how well do you want it to perform after you install the update?
cheers
EDIT: i just assume everyone accesses recovery and download mode so i didnt post the button combo. recovery is: Volume Up + Home + Power. release just the power button when you get a vibrate.