Any lag or heating issues?

Zero lag for me. Been using it for two weeks now and haven't noticed ANY kind of performance issues at all. It runs like a dream, in fact as good as my wife's Zenfone 2, which probably is the smoothest running phone in the market.

Heating is there but not to an extent that it becomes a bother. Using the phone while charging specially seems to make it hot. General purpose usage, I dont see any real issues at all. All smartphones get heated to an extent if you run demanding software. That comes iwth the territory.

I have the H959 version with 2GB RAM. Flawless performance and I am not exaggerating.

I do not qualify as a "power user" though.

Most of the performance issues with the phone were sorted out through updates. The carrier branded versions are still showing some issues though from what i have gathered from reading online.