Asus has done a great job with their Zenfone series. I have been using the Zenfone 2 ZE551ML and have found nothing much to complain about.
The looks are premium, the volume buttons are well crafted and the dual flash strong enough to light a small sized room pretty well.
The display is awesome( 1080p, full HD) , and the sound quality above average.
The battery backup is good, a fully charged battery can last upto one and a half days on medium usage and upto two days in the power saver mode.
Performance is okay, the phone does not hang often, and it can multitask quite easily.
The camera( both front and rear) is quite good in this device and it even seems to manage low light photography( with effort, though) . The pictures though, even in high quality mode seem to burst when zoomed in.
The phone comes with plenty of inbuilt apps, which maybe annoying to some as they slow down the device. Nevertheless, they can be disabled and enabled whenever desired.
Also, the software updates provided by Asus are quite good and enhance the performance every time they are installed
At this price point, it must be said that Asus has done a fine job with their Zenfone 2 ZE551ML. This phone has several capabilities that can take on even the smartphones that are a premium to its class.