Updated last week, so for, the only issue I am having, is with text messages. Unless, of course, I use the stock messaging app.
So with the stock messaging app you have no issues, but when you use a third-party app you do?
KitKat only allows for one messaging app to be "default", and the default app can only do some things, like sending messages... if you want to switch the default app, go to Settings -> Tethering & Networks and scroll to the bottom, there is an option called "Default SMS app", tap it and select your messaging app. Note that some apps like Handcent and Textra (maybe more, I don't know personally) don't like the switch to KK from JB... Backup your SMS with
SMS Backup & Restore (shouldn't need this really, but to be safe), set Messaging as the default app, go into Application Manager and clear data on all non-stock messaging apps then uninstall them, reboot the device, reinstall your messaging app, go into settings and make it default, then start the messaging app and see what happens. If you need to restore the backup, reset the default messaging app app (SMS BU&R will make you set it as the default app so it can write to the SMS database), and start it and be patient (if Hangouts go into SMS settings and import messages)... Depending on the number of messages you have it might take a while for them to show up, I have about 7000 messages currently and it takes about 5 minutes for them to initially show up in Hangouts after a full restore.
Remember only ONE app can be default, meaning only ONE app can send messages, no more bouncing between different SMS apps on the fly like in previous Android versions... it's a KitKat security "feature" and will not be "fixed" since it is not broken but by design.