The stats on my iPad 3 are brokenstandby time also counts up when I'm using the device, rather than just on standby.
What I have found though, is that battery life is considerably improved. On iOS 5, I was getting maybe 68 hours, and now it's more like 812 hours depending on usage and brightness. (sometimes more, even)
I do think that a lot of it probably has to be that they've finally squashed whatever battery-draining bugs remained in iOS 5 though. Even on the latest release, I would still have idle CPU gradually increase up to about 20% over time if I didn't restart the device.