I've had my phone on for 16 hours now and my battery is at 50% (though its probably close to 40% now). I keep the phone on power saver mode because i'm indoors most of the day so I don't need a high brightness setting. I have data sync running in the background but I shut off WiFi when I dont use it and I dont use GPS or Bluetooth. I keep 3 widgets running in the Weather Channel, which I set to only update one location instead of following me. I also use Twitter and Facebook and have them update every 2 hours. According to my Battery Use, about 50% of my battery has been used through voice calls totaling over 30 minutes.
I have been moderately active with my phone today. I probably have spent about 30 minutes surfing the Internet, and another half hour in the Market downloading about 10 applications or so. I also had about two straight sessions of texting, one for about 45 minutes and the other for about 3 hours. I have ATK installed but only to kill the non-essential applications which eat up memory such as Pandora or ESPN ScoreCenter.
I know my usage maybe light in comparison to others, but I find the phone is just as enjoyable even without the constant updating through the widgets. Widgets are nice, but this phone is fast enough to justify not having widgets and just opening an application when you actually want to use it and not have constant updating. The peace of mind of having a battery that lasts all day is worth it to me to not go overboard with applications and constant data streaming.
When I first got the phone I was new to Android, and this was my first smartphone so I naturally overloaded my home-screens with all types of widgets and had them constantly updating me with whats going on, but after 6 hours my battery was down to 20 or 30 percent. After taking it down a notch (or three) I have found that the battery lasts much much longer, and not having the constant updates was worth the peace of mind of not having to locate a charger. Try removing all the flashy widgets and updates for a day and see how the phone runs and how your experience is without them. If you prefer having the constant data streaming for instant updates, then i suggest buying another battery to keep handy. Also, I found that Auto-brightness killed my battery a lot faster too, so I set my brightness to 20% and that does the trick for me.
Note: This post wasn't really directed at the OP, but to anybody who desires to maximize their battery life.