I own D2G for about a month now and pretty much finished all the setup.
I was initially disappointed by poor battery time but not completely since my first Droid1 also had poor battery life in the beginning.
I tried several method and now run time improved quite a bit. So, I am trying to share my method and see other folks have better idea.
1. I changed to extended battery. I ordered from Verizon. $37 with corporate discount. Door included. This seems to improve 30% as spec states.
2. Changed Network mode to CDMA only. I don't know how much it improves but I heard from my friend who work for Modem chip that mode switching consumes quite a bit between CDMA and GSM/WCDMA. CDMA only mode searches CDMA signal when reception is poor. Global mode searches everything when reception is poor. If you are in downtown with good reception, this might not help.
3. Use only Push email. I have company email and gmail. Both support push so phone doesn't need to wake up every 15 min to check email. I have Yahoo account as well but I use google to download email from Yahoo. So, Google checks yahoo every 15 min and deliver to my phone when there's email.
4. I purchased Jrummy's overclock app. This is not to overclock my phone. This is to use ULV kernel. And also, I created profile to reduce clock to 300MHz when screen is off.
5. I use Timeriff to auto adjust phone settings. At home, I use wifi. when I drive to work, I created profile to turn on bluetooth, turn on auto brightness and turn off wifi. About the time to arrive at work, Timeriff turn off bluetooth and reduce brightness to minimum. While I sleep, it also turns off wifi as well.
6. Turn off auto update for twitter and facebook. I update manually. This also helps to reduce idle power consumption.