Indeed. 12-13% in 8 hours, or about 1.5% per hour, is what I have been experiencing for the past two years. (That is when idle. When in use, such as during a browsing session, it is more like 1% per minute.) Unlike atlochowski, I have not observed any difference in any of the 15 or so OS updates during that time.

I absolutely agree with Dave that it is bad. My previous phone, Treo 600, lasted 8-9 days on a full charge. Of constant use, not idle. But there was no WiFi, so I am not sure how fair that comparison is.