I know it's too early to talk about this but iOS 7 will have a large effect on the battery of your iPhone/iPad. Like every iOS upgrade, I'm sure we're going to see a lot of people complain about poor battery.
The features on iOS 7 are quite power-packed and no matter what Tim or Craig or anyone says, the battery will be compromised for the sake of seamless performance. Most notably because there are a lot many features that would be running consistently.
Let's take a look at where the impact comes from:
- Background tilt feature which continuously monitors the gyro
- Real-time clock
- A more powerful camera this time; coupled with a powerful Photo app
- New graphic displays in Safari tabs
- Multitasking will have an impact
Two things: firstly, these are just the tip of the iceberg because these are the user-facing features. There are a ton of processes going on behind the screen and that's where the whole key lies. And secondly, some might argue that these consume tiny resources (for instance, the clock) but pile up a lot of tiny resources one over the other and we've got a bunch of stuff that eats up your battery pretty fast.
Developer Betas are always problematic when it comes to battery so whatever you hear about the battery right now (at least till the Gold Master version) won't stick around for long. The developer beta versions almost always gobble up the battery.
When the final iOS 7 version is released, it will run on a device with the same battery capacity. (Unless of course there's the iPhone 5S which, rumors say, has a larger battery capacity.)
Now in iOS 6, there are very little drastic changes from that of iOS 5. Even then, there have been umpteen cases where the battery has run amok.
There isn't a particular solution as yet. You might consider buying and using one of those iPhone battery cases because they have a profound impact on increasing the battery life of your iPhone.
Given the ability to configure a lot of stuff, users can turn off the toggles on things like wallpaper tilt, multitasking theme etc. We'll of course have to wait for the final version to figure these things out.