With my iphone, it would show standby (amount of time since last unplugged) and actual usage. With my droid, it only shows amount of time since last unplugged. Any app that shows actual usage?
You should look at Battery Indicator ProDroid in the market - this is a paid version but I believe there is a free version. It shows you battery remaining and time since last charge. It also allows you a shortcut to the usage menu in your phone settings. It has a taskbar icon that also shows percentage remaining. I have been using for a few days now and it seems fairly accurate.
Not sure if this is exactly what you need but there is an app called JuicePlotter which shows a graph over time of battery % and goes back as far as when you enable it I am pretty sure.