Been doing a little testing and here's what I'm getting.
First the setup:
Stock Nexus One on AT&T, about one month old, Originally with Éclair 2.1 update 1 then manually updated to FRF83 then got the OTA to FRF91. Using AWDLauncher with 5 home screens and the following widgets ... Stock media player, stock YouTube, Google calendar, Google search, SwitchPro, The Weather Channel and Beautiful Home. Screen brightness set to Auto, 3G on all the time as is GPS. WiFi off unless needed as is bluetooth. Push email checking 3 POP3 accounts.
Currently loaded apps are Task killer, SwitchPro, Voice Search, The Weather Channel (yeah, I am an aging weather junkie, so sue me... oh and don't forget, all you kids, stay off my lawn, too) Amazon, Email, Facebook, Clock, YouTube and Gmail. 212M available.
Charged battery to full from 10% and unplugged yesterday morning. With relatively light use as summarized. Showed a 6 minute YouTube video to a friend (iPhone vs. EVO cartoon), sent and received some texts -- maybe 20, checked email at least every hour, installed two apps from the market, browsed for a total of around 45 minutes and had 30 minutes worth of airtime on actual phone calls, oh yeah, took 4 pictures, too and took the dogs out to pee using the LED as a flashlight (5 minutes, tops).
This picture was from about a half hour ago.
As you can see it was on for over 28 hours and the indicator said I had 25% charge left. I am now approaching 30 hours, after using the screen for most of that time to review the widgets and running apps for the lists above and it's down to 23%.
If this continues, I will be a very happy camper.