Clockwork Mod 22.214.171.124 installed on my S4 mini.
been using cm-11 for a few weeks
tested cm-12-20141129-UNOFFICIAL-serranodsdd.zip and cm-12-20141130-UNOFFICIAL-serranodsdd.zip
Here's my report of experiences during testing in the hope it helps with the debugging;
Camera app worked well
Wifi works (I was able to download any apps I tried without issues gapps, facebook, viber etc)... wifi code remembered after reboot
Mobile data works (On at least one SIM did not check other... I believe original Samsung S4 only had 3G in one of the Sims)
MP3 (google play music, apollo)
Storage (detected internal and external)
Battery seems stable
Bluetooth works partly (Pairs headset and can listen to audio through it. However when I tried to call the sound went to phone speaker even though option was ticked to send both music and phone audio to headset.)
Dial App (hanging and bugging Wait or Force close option appeared every time)
Name of Sim cards forgotten after reboot.
System update (Check update says latest is applied, don't this it's doing anything though)
Pin Screen (You can go into security an pin the screen, unpinning not possible, reboot unpins)
Android 5.0 in general seems to work smoothly... Google Now has a white background... seems a step backwards to me (harder on eyes and have heard is also a bigger drain on battery... not sure if true). I tried installing the Trebuchet Launcher from CM11... installed but did not function as expected. I downloaded Nova Launcher and this solved it. Z launcher beta from Nokia is also a nice change. In general the notifications of Android 5.0 are an improvement and the overview of open apps is an improvement. I've restored CM11 for now... the dialler issues would prevent me from using CM12 till resolved.
Thanks again for all the dev work. Above is only intended to support testing, not to criticize.