I have found three annoying issues.
3. Messenger box in lock screen. This used to be optional, now you get a box no matter what. You can turn off "preview" but this also turns it off in your Notifications bar. I ended up downloading a different messenging app and changing the default to that one instead.
Discussing the GS4, from Need Some Help with Lock Screen Notifications ? Samsung GS4
"•You can download a root file browser like ES File Exploxer from the Play Store,
•Go to System -> App
•Rename: KeyguardWidget.apk to KeyguardWidget.apk.bak
•Reboot your device."
Would this carry over to the GS3 as well, both running Kitkat?