I've said it before, but compared to the power requirements of my old PDA when using wi-fi the N800 power drain with wi-fi is near non-existent. It doesn't seem to make a difference if I have wi-fi connected or not, at least the battery is still full at the end of the day (sitting idle on the desk, the rss feed checks in every 30 minutes).
Even when actively using wi-fi (browsing and the like) the drain isn't anything like I was used to from the PDA.
In short, it's good..!