Updates via Kies are non-wipe. That said, no guarantee that you would not encounter problems requiring a wipe and factory reset later. Apps not working properly, phone reboots itself, wifi or 3G not working. There are those who report having no issue with the update though. So it depends on your luck.
Before update, back up what ever you can. Maybe uninstall any non play store apps and maybe non-essential apps, then update. If problems crops up, you can still do a factory reset.
Yeap.... indeed ....
I was hoping to avoid the common problems and at first everything was ok. Except for charging via USB, which stopped working.
Two day down the road and my WIFI would take for ever to connect. The icon is green as if it was connected, but it doesn't show the small icon on the notification bar. So today I did factory reset and now it works great.
Also, charging via USB came back and works without problem.
I must say, I had my Google set up to back up my apps and settings, and after factory reset, it did great job getting most of my stuff back. Some apps had icons but where not installed, these are the apps that I had to register on line in order to download (paid apps). Some worked like charm and were reloaded with all the preferences. Of course, whatever apps are using SIGN IN stuff, like Instagram, FB etc... you just need to re-sign in.
Over all, about two hours restoring and setting it back to the way I like, but now it works really really smooth
By the way, you can always copy your phone folders to your computer. Then overwrite some of the settings using your copies. I did that will bunch of widgets. Some of them are tedious to configure, like Minimilistic Text. I back up my setting, then just copy paste to the backup data folder of that widget upon restore. It's less tedious than it sounds really.
Most important, phone works great now.
cheers
Seba