Actually. I haven't noticed the notification LED yet.
Battery life is awesome like always... if you currently don't have awesome battery life, better look at that. An upgrade won't fix it.
I sometimes have the LED problem, but can't pinpoint exactly when.... sometimes after an SMS and other times after a Whatsapp message..... is however annoying :-(
My battery life is OK, much better than my previous S3 - I just heard there was a Doze mode in the new firmware, that was supposed to improve life even further