My screen is at the lowest brightness setting and I'm using a predominantly black screen with LeeDroids lower auto brightness fix, I didn't keep the screen on for any extensive youtube watching or surfing. Listened to music, checked and updated FB/Twitter/gmail regularly (sync every hour), read through the xda forum, LiveProfile messenger on and checking for messages constantly, checked online banking, filmed my kids on rides when out in town and took pictures of them and as you can see made plenty phone calls (with Call Recorder on I might add which is known for big drain which took it above display). Average normal use I'd reckon.
When I'm hammering the phone I can easily manage 23 hours espesh with me hardly putting it down playing games in my 10 hour shift at work. I know if I'd left it alone full stop it would have matched my standard Desires 4 days untouched.
My wallpaper and homescreen for comparison...