I just got my Maxx on Thursday. I got it, charged it to 100%, and got these stats:
Total Time: 17 hours and change
Screen On Time: 6 hours and change
When I put it on the charger, it still had about 10% left. And those times are all reflected with all the downloading of apps, system updates, contact/account syncs, about 5 minutes of voice calls, pics/video, playing with the phone, etc. I will say that those numbers were all achieved on wifi though.
I just put it on the charger for the 2nd time w/ about 22% battery left, and here are those stats:
Total Time: 31 hours (approx)
Screen On Time: 3 hours and change
I'd say about 70% was on wifi, 30% on 4G, give or take. I threw it on the charger a bit early this time, but have no doubt I could have tagged on another hour of screen on time and another 5 or 6 of Total Time before hitting 10%.
So, if battery life is important to you, the Maxx is a good choice. On day 3, I am quite pleased that I went with the Maxx over the Rezound.