The jury is still out on whether battery life under iOS 5.0 is the same, worse or better than in previous builds of the iPhone, iPad & iPod Touch software.
In the meantime, if you are experiencing much faster battery drain, there are a number of things you can try.
Firstly, makes sure you only have notifications set for the apps that you really want notifications for. Sounds obvious I know but notifications are generally set for way more apps than you will typically want or need notifications from.
The same can be said for location services. You will find a lot of apps with location services turned on. Go through them and turn off anything you don’t want to use location. At the bottom of the location services settings screen tap on System Services and turn on Status Bar Icon. This will show the location services arrow in the status bar whenever one of the system services is using location. This will give you an idea of which system service is potentially draining your battery. I found that the time zone setting was the biggest culprit here and have since turned it off.
Finally, and I’d actually recommend doing this first, carry out a full charge cycle of your device. All that means is run the devices battery flat, to the point that the device turns off. Then charge it back to 100%, ideally without interruption to the charging.
Why charge cycle the device? After such a large update to the operating system software, it often needs to re-learn the extremities of the battery charge (it’s lowest and highest charge levels). The software learns this by depleting the battery fully and then charging it back to full.
I reported an issue with the battery draining rapidly on my own 3GS. Take a look at the screen grab below of the battery usage settings screen. Pretty dire eh?
Despite turning a lot of the notifications and location services off, 9-10 hours was the most I could get out of it. However, after giving the battery a full discharge, followed by a full, uninterrupted charge to 100% I am happy to report that battery life is back to where it was prior to the update.
So, first port of call, should you be experiencing poor battery life after updating to iOS 5.0, is to charge cycle your device.