I switched to ART right after I updated to 4.4 in December. Once the runtime setting is changed from Dalvik to ART, the phone will reboot and take pretty long time as it needs to compile all apps. After that - pretty smooth sailing. The phone is quite a bit snappier and the battery life is crazy great! The only issues I've ran into is Pandora needed to be uninstalled and reinstalled - after that works great. The only remaining issue I have while on ART is that Facebook cant post pictures - I can live with that. I'm staying on ART.