Generally after the PR upgrades the battery usage is increased for maybe a few hours(tracker or something like that) plus when people get a new phone they tend to play with it a lot more than later on when the novelty wears off a bit, so probably not so surprising about the initial battery usage.

One tip is finding a balance on how often feeds like facebook or anything else update with power consumption, plus use wifi over 3G when possible as its more efficient.

Go to settings - Notifications - Feeds on home screen to turn off facebook news feed (friends lame facebook apps get ridiculously annoying very quickly). There's a feeds option in Settings - Applications - Feeds as well.

Try navigating your N8 or any other phone for that matter after using your N9 for a week, they seem so old fashioned.