I've had my AT&T Moto X since it came out. Got the 4.4 update yesterday and immediately noticed lag others have reported. I tried the ART runtime which improved performance but RunKeeper's GPS didn't work and I use that app so I did a factory reset and went back to Dalvik. No more lag after the factory reset (it reset to 4.4 unfortunately, was hoping to go back to 4.2.2). HOWEVER battery drain is a real issue. I've had this phone for over two months so I know what is abnormal and 4.4 is sucking the battery dry. sent a text to my son, battery was at 70%, 35 minutes later with hardly touching the phone it was down to 56%. That is NOT good. I called AT&T and they are willing to send me a replacement (same custom colors so they say) but I'm going to give it a couple of days and AT&T is supposed to call me back Monday to see how the battery issue it.
Any suggestions would be appreciated. I've already turned on the battery saver feature and set brightness to AUTO, both things I didn't have to do on 4.2.2.