I am having the same issue. Woke up yesterday morning, unplugged my phone from the charger, set it aside while I got ready for work, didn't use it at all until I got in the car to go to work, 20 minutes later I arrive at work and it says 43%. So a total of an hour and a half with minimal usage and it drains over half the battery. I tried using the work around in the developer notes and it did nothing.
I was actually a little impressed with Beta 3 up until this point. I was not plagued as badly with the sudden phone shut down from "low battery" at random percentages like 22% or even 37% like has been happening to me and so many others since the introduction of iOS 7. Before I could run my iPhone, any one of them, on all different version of iOS, right down to 1% and it would hang there until finally shutting down. With iOS 7 and iOS 8 beta 1 and 2, it would die at random percentages. And I would sometimes plug my phone in at say 8% and it would immediately jump to some like 17% or 23%. Beta 3 still isn't iOS 6 or earlier, but it hasn't shut off at anything above 10% yet.