I received mine on Friday (via pre-order), coming from an Samsung Infuse I'm in heaven right now. I too am somewhat concerned about battery life as my Infuse would drain a battery in about 4-5 hours. So far the S4 is showing good results as far as the features (gestures) the phone came with some of them turned off so I watched a youtube video (How to set up and use Air View and Air Gestures on the Samsung Galaxy S 4 - YouTube
) that showed me how to enable them and use them for the most part.
The only one that I was only able to use once and I haven't been able to engage since was eye scrolling. All the other's are pretty cool!
I wanted to wait to see what was the deal with the 32GB model but it appears to be MIA or a cruel joke!