I'm also quite satisfied - the performance, screen, cameras, size of the phone it is all superb, working as a charm! Fortunately didn't have those big problems regarding the proximity sensor (happens only sometimes, very rarely) or freezing etc.
However there are two things that could be improved:
Battery life;
VoLTE and VoWIFI support - I know that these two are also dependent on the carrier but in my opinion Asus is not doing enough in this matter (recertification, improvement, putting pressure on the carriers etc.)