I bought samsung s3 few days ago even I was so worried for its battery performance.but after rooting my phone it solved my problem now my battery gives longer life. After installing greenify [officially rooted app] battery saver app from play store, battery is longer than my rooted phone. So if you are really concerned about s3’s battery packup I suggest you to root phone and install greenify app and enjoy. If you dont want to root your phone then also you can install this app or install deep sleep battery saver and increse your battery life for some extend.
My S3 came with JB 4.1.2 and the battery life is actually flawless. Been using for almost 2 years.The device is mega fast and snappy. It does lag occasionally when handling a lot of operations, but what can you expect from a 1 gb ram phone released in 2012?
The screen has splendid pixel density, and is very beautiful to look at. Flawless sound. I love my S3:D.Yes, I do wish Samsung released a newer android version for the S3. Those custom ROMs with lollipop, etc just hamper battery life and are all unstable. Other than that, I really do not understand the opinions here. Battery life on S3 with stock 4.1.2 is superb and lasts even longer than the 2600mAh+ phones, even the iphone 5s, which my friends bring to college.