The most obvious problem with LP and MM bl/modem on KK is the GPS being broken, absolutely dead. Besides that I've had several lost calls and SMS, some reboots and worst battery. Go to http://www.sammobile.com/firmwares/ , search for your last KK developed ROM and see what bl/modem is using.
i m very sorry..but i'm on the latest pa1 ( from sammobile, vf nederland ), downgrade from LL, , now on 4.4.4 latest nightly ( 08.02..)
best batt life ever, no single issue with wifi, gps..etc, 3 days batt + 4 hours SOT..
maybe i'm lucky..
clean flash. btw.