Hi. All android devices heat up under heavy use. My G3 only heats up when playing HD games. There is abit of lag in the UI but that can be fixed by speeding up animations. Battery lasts a one & half days on average usage & a full day on heavy usage. This phone is a bargain & has alot of features for the price. Mine came with Lollipop & I have no issues.
People are complaining because they comparing it to this years flagships which you cant. If you want the best then buy a 2015 flagship.