I've come across something that may be good to know if you've set up a Hotmail/Windows Live mail account in your phone.
There are 2 ways you can do this: creating a Social Hub for Windows Live account, or creating an Exchange ActiveSync account. Both methods work, but there appears to be a bug with the ActiveSync method that causes excessive data usage and battery drain. There's a thread on XDA about it.
I only found this out because designgears has removed the social hub APKs from Cognition S2, and I switched to using ActiveSync because of that. My battery life is now about 2/3 of what I was getting on stock XXKG1.
I'm going to put the minimum Social Hub stuff back on and will see how battery usage changes.