I had 18hrs 40mins of up time and 5hr 15mins of screen time. 3G/WiFi mode, Stamina mode OFF
Usage includes web surfing, facebook, messaging and video playback (1hr).
Don't worry about the brightness. ZU at 0% is brighter than S4 at -1 (lowest is -5) lol. ZU really had a bright screen.
Current Device: Sony Xperia Z Ultra
Past Devices: Samsung Galaxy S4 LTE (I9505), Samsung Galaxy Note 10.1 LTE, Samsung Galaxy Note 2, Samsung Galaxy S3, Samsung Galaxy Note, HTC Sensation XE, HTC Desire HD, HTC Desire Z, HTC Desire