I had been using this phone for the last couple of days and below are my comments. These are not very detailed but just thought would post which may help your decision making process.
Pros:
Screeen - IPS makes it stunning than many of the other flagship models as well Z1.
Processor - Ultra Fast due to 801 Chipsets. Never hangs or heats up.
Ram - 3 GB ram which makes the device super fast.
Weight - Extremely well built and you really feel this phone lighter even in pockets.
Battery - 3 Days in Stamina Mode(very useful) and 1.5 days on normal usage with 3G, Listening to songs and other regular activities. No problems faced. Very impressed.
LED Indicator - Well placed and very useful.
Sound Quality - Amazing with and without headphones both for calls and audio.
Wireless connectivity - Awesome.
Con’s
Nothing much.
Some may feel the phone to be little larger, this definitely smaller than a Note 3.
Smart band
Very useful accessory that can track every moment of your life.
Getting used to it only now.
Tracks how much walk, speak, listen to music, sleep, burn calories etc etc. very useful if worn 24/7.
This phone is definitely worth the investment against the other flagship models that are currently available and this includes S5 and HTC M8(One 2