Lumia 520 (AT&T)
From my Insider app, I can get an estimated 36-40 hours based on my usage. Just light email checking, Metrovoice checking for texts and a few apps. No video streaming such as Youtube or gaming. I have Wifi, Bluetooth, Data always on, medium brightness, and going back and forth between double tap to wake. I'm on wifi at work and home. The only time I use celllular data is when I'm commuting. When I'm at home, I use my desktop primarily for texting, web surfing, email, Youtube, listening to music, etc. Don't do a lot of talking on the phone. Overall, I'm happy with it, but I haven't tested it with heavy usage. I'm sure GPS will drain the battery quickly.