I am on a p6810, wifi only version, i installed the nano open gapps, along with supersu beta 2.52 initially and haven't experienced any freezing. I got the latest gapps build for Android 4.4.
Have you got an sdcard? Try removing it if you do as I have found that sometimes a faulty sd card can be the issue
I'm currently on CarbonROM 5.1.1, and although it's pretty snappy it still feels sluggish even with overclock and a different I/O. 4.4.4 just seems like the way to go on the P6800.