Maybe a relevant post here. I've got my 4, touch and pad 2 upgraded and at times see battery life go down rather fast. The iPad is usually used for reference material and newspaper apps, sometimes my kids play games. It's burning the battery faster no matter what but this AM a customer asked me a bunch of questions via iMessage and a few more came in. I was down 12% battery in no time.
Originally Posted by Jeffnucci
So here it seems like features of iOS 5 are draining the battery faster and maybe even faster when iMessage is used.
It's only been a few days but my phone's at 20% faster too. I just looked at usage and a bunch of iMessages were the main difference between Friday and Thursday use.
It's clearly got smarts that a text message doesn't have. I see it shows when the other party is typing, syncs across devices, and shows messages delivered so my guess is more use of radios, CPU, redrawing the screen etc..