I also tried this after getting my new 1800mah battery:
Taken Off Of the XDA Forums,
1.) With the phone ON, charge till the reported battery status is full/green LED.
2.) Turn Phone OFF and then charge until LED turns green again.
3.) Boot to recovery mode and go to console (or adb shell) and type:
mount -a
rm /data/system/batterystats.bin
You can also remove this file with the "Root Explorer" app from the market.
4.) Once the file is removed, Power the phone off once more and charge it till the LED is green, then turn it back on. Once at the homescreen, unplug it from the charger and then use it until the battery dies completely. (phone will shut itself off)
5.) Charge it fully again.
After this, you should notice you now have better battery life.
I did this yesterday and charged the phone overnight. I unplugged it this morning before I left for work. On the way I send/received about a dozen emails (Gmail and Exchange), some text messages, two phone calls and checked the weather. When I got to work I was something I thought I would never see on my phone:
Unplugged for over 2 hours and still sitting at 100%
Just thought I'd share.