The beta 3 update for my iPhone 5 has way better battery life than it did on 6.1.4. Been off the charger for 2 hours so far, pretty good use, only at 98%.
Yeah I get better battery life on wifi (of course), but 3G was absolutely killing my battery on iOS 6.
Throughout beta 1 + 2 I have had to plug my phone in before I leave work (workin' 9-5 (what a way to make a livin')) or in the car on the way home.
Beta 3 is too early to tell but I'll see after today.