Hi - add my piece here regarding ART runtime. I switch mine on over 24 hours ago and have noticed the battery is giving better results, after average day of use I was on 70% that night. Battery still drains as usual with constant use though. I have had no freezes as yet, and it seems to run pretty smoothly. Model: D855 International
I run TweaksBox LG G3 and have also modified speaker boost and disabled that annoying LG jingle on shut down and boot up.
I have switched off 'fast dormancy rate' - still not sure what difference it will make. Haven't noticed anything yet.
To speed transitions I set all animations to 0.5 but it seems a little too snappy so I switched back to 1x.
Update Edit: I admittedly had a placebo effect. I have realised that my phone is being forced by Xposed Framework to remain on Dalvik. Every time I selected ART it reboots back into Dalvik and after some reading found that Xposed on my rooted G3 is unable to run on ART so effectively blocks it.