I purchased Iphone 6S about 1 year ago.Till now no issue in performance compare to other phones which I used in past.
There are some hidden features which I learnt after using it. Battery backup is more than 24 hrs if you are not watching aby videos for 8-7 hrs.Battery charges in few minutes even if battery is completely drained out.
I preferred Iphone 6S gold for which I paid 4000 extra but if you are not fond of colors then do not spend 4000 extra in buying Gold color.Camera is amazing, 3D touch feature enables me to read any message with just one touch.
Good phone