I've got a good feel of the battery life after a couple of weeks of using this phone.
Compared to my Bionic, the battery on this phone last incredibly long. I would estimate that it lasts more than 3x as long. My Bionic could only last around 8 hours of moderately heavy use (watching videos for 30 mins., listening to MP3s for 4 hours, etc.).
This phone lasts a good 3 days of moderately heavy use. I've averaged about 1 day & 15 hours with 15% battery left. And that's with LTE. I'm very happy with the phone.
Keep in mind that my Bionic battery was probably beaten-up pretty badly. I am pretty sure it lastest noticeably longer when I first got the phone.