I thought I give it few days and see how it works compared to other ROMS.. I tried Validus and had few bugs with ring volume not working and standby mode.
So far I have not found any bugs with CM12, runs super crazy fast, all my apps work, Bluetooth is even better than LG, reconnects automatically.
The only feature that I would like to have Auto switch in Data, like in LG it switches automatically between 2G,3G,LTE, this is missing in CM12 but I guess not a big deal (maybe can find app for it.)
Battery is great, maybe just tiny better from LG.
Contact list I way better with almost full screen picture when you dial someone.
For some reason cant play WAV files, player does not support it, will try to download other player.
CM12 is already rooted, you can enable/disable it in Developer options to use some other programs.
What I suggest to get:
In LG my icons were bigger which I really liked, in CM12 apparently you cannot make them bigger, everything is smaller but I installed Nova Launcher and even paid for it cause I really like it, you can enlarge your screen and everything is back from what I used to like, you can do so many fantastic things it is unbelievable, I highly recommend it have it installed.
Get Power Toggles!!!!!!! freaking great, makes your life easier.
Don't like camera, missing 4K. but I found better one which I really like and found it on some other forum. Don't remember where I download it but here is zip file you can google (MotoAppsMaterialAOSP.zip) and flash with TWRP.
By the way make sure you have backup and recovery TWRP version 22.214.171.124 the only version works with D852, don't get the latest.
It saved my life, I almost **** my pants few times and had to recover the phone. If you do not have this installed DON'T EVEN THINK ABOUT INSTALLING ANY ROMS!!!. there is high chance you can screw this up and all is left garbage bin.
For now I leave it like this because it is really stable, not planning to install later CM12 nighties, for 2 reasons: afraid to make it worth and because I am tired reinstalling apps.
If you are looking to upgrade your phone to a lollipop version and have it as close as LG I really recommend the same setup I have. it is worth it.
If you want to know how to do it you got to google first how to root, install recovery, make back up, the rest is easy. Just watch plenty youtube videos.
By the way to boot into recovery mod on LG G3 here is how (turn it off--> press volume down and power--> let go after you see LG logo, then press power and volume down again) after that you should see TWRP if you have it installed correctly.
I also uploaded small video on youtube what I looks like, I cannot post link on this forum, but if you search on youtube for user "ukrik" it will be there.