There are some UI hiccups with this phone.... LG completely overhauled the interface and loaded it on a display that has a MUCH higher resolution. That the UI has some optimization issues on first phone launched with that combination isn't a surprise. It's not a hardware limitation either... I did some side by side stuff with my wife's Nexus 5... and sometimes the Nexus would beat the G3 to the punch, other times the G3 would zip though a half step quicker. A hardware limitation wouldn't be intermittent like that.
Running the AOSP builds, which also eliminated those burps reinforced that belief. LG's Optimus UI, in G3 clothing, needed a little bit of work. And I can say, without a shadow of a doubt, that the issues can be addressed because they HAVE been addressed. I've been running CloudyG3 for a few days now and it's UI performance is on par with the G3's AOSP builds AND my Nexus 5 reference device. So either CloudyFA is some android savant and did more to optimize the G3's software than all of the engineers over at LG, or the international 10M base which Cloudy is based on got the framework updates that addressed the problems... .and us poor saps here in the US just haven't got the new code yet.