Background: I am a long-time user of ASUS computer components and miscellaneous add-on cards. This is my first 'completely built' product purchase from asus. This phone is to be used by my mother.
Why Zenfone?
The primary reason for buying this phone was that it supported
Front Camera
Proximity Sensor for calls
Good (AF) camera for daylight photography (1080p video)
GPS chip! (the 5.5k galaxy star pro lacks this and has only 512MB RAM)
Smooth UI with latest Android
Not much options in the 6k bracket supported these features. The Moto E came close but it lacks a front camera and AF on the rear, which were a deal-breaker for me as she wanted those features.
Overview, performance
This phone supports many new features on the camera and new apps for the segment. It has the party share feature to quickly transfer pics to nearby devices. The camera is very good in low light and has a host of features like background reduction, HDR (realtime) and timelapse modes. It has good performance with no lags in the UI till now. I haven't tested talktime on battery as I lack a micro-sim card to put in the device. There are no overheating issues as described on the forums and it performs flawlessly.
The phone feels nice to hold and is very light. The screen has good contrast and vivid colours. The premium finish beneath the screen and the rear cover make it look like a phone worth well upwards of 10k. The rear cover fits snugly and no gaps are to be seen on the sides. Volume and wake buttons have a ridged silvery finish adding to the premium-ness.
A few gripes/issues I with the phone (as an Android user ) Intel x86 platform - Limited custom ROMs and uncertain update beyond Kitkat. PowerVR SGXMP 544 is not going to last much for modern games.
Awkward button placement - Volume and power key cluttered together like Micromax. Accidental presses of volume key likely when your intent is to wake the device
Weak speaker- Speaker is a very feeble one and disappoints with everyone asking
Volume full hai kya? Difficult to open the battery door- The door has only one fingernail inset and the door is so tightly clasped that prying it open makes strange sounds. Careless removal might break the battery door, I fear.
No button backlight - This is my chief issue with the device. Even if it lacks an ambient light sensor, the least asus could have done is to provide continuous backlight for the capacitive buttons. What if I have to use my device at night

? I suppose onscreen buttons will be made available as a mod.
Long press recents key to make it work as context menu key- Really, this should be the other way round
Inverted MicroUSB port - This is likely to cause blunders as all of our other devices have the port the other way up
I bought this device for my mom despite the intel x86 quirk as this was not pertinent to her kind of usage. The other quirks were discovered during a short usage period of 6 hours.
Pics in no particular order
Quadrant Score
AnTuTu Score
Some more things
You can set the long press of
recents key to take screenshots. No more doing yoga with the power and volume buttons.
There is a tiny multi colour notification LED by the earpiece.
Comes with
Android 4.3 and after a 70MB minor update, a clean master' esque RAM liberating app is preinstalled in quick settings. Neat!
Has power-saving profiles built in with presets for games, music etc.
The whatnext app is somewhat like google now. It tells you the weather with advice like " take a raincoat tomorrow, thundershowers predicted" and reminds you of tasks. It also has a widget on the lockscreen.
The camera is the biggest takeaway of the device with oodles of features. It performs well in low light with limited noise and has vivid colours for a camera lacking flash. I expect it to beat the Moto E hands down on this aspect.
The compact charger is rated 1300ma charging current, larger than the Nokia 1200ma one I have now. Charging is quick. Data cable doubles up as a charger cable.
All
voice calls can be automatically recorded and saved to SD Card, if required.
There is
no secondary microphone for Noise cancellation.
Both SIM slots are micro-sim.
Video recording is set to
720p if video stabilization is enabled in camera UI.
No spare battery provided like the Malaysian counterpart.
The package lacks a headset.
Flipkart lists another variant Zenfone 4 with 4.5 inch screen, 1800MAh battery and 8MP camera for 6999 as "coming soon". Other specs remain the same.
Conclusion
The phone was bought despite the Intel badge because it satisfied on the counts listed in the beginning of the review. This device is trademark ASUS with a solid build with nifty software enhancements and and stunning looks.