Why did my battery usage on 3G grow with the Android 2.3 update?
"cell standby" = "background sync". And if your Wifi turns off on screen off, apps will use 3G instead.

You might want to check your Wifi policy, which is hidden in the "advanced" menu: When in "network &amp; wireless" -> "wifi", hit the menu button and select "advanced". Here, switch your Wifi policy to "always on" -- so it will stay on when the display is switched off, which means no 3G fallback as long as Wifi is available.

I've read about this issue a couple of times, and many report setting the Wifi standby policy as described above largely improves the situation.



UPDATE:

I obviously wrote bullshit here. I left the bullshit in (but striked it so you can see where I was wrong). Closer investigation brought me to this: What is Cell standby and how can I keep it from eating my battery?.

So basically my reasoning here was wrong, but luckily the recommendations still match somehow :)