Android - How can I tell what is really draining my battery?

Try out an app called Watchdog.

It monitors your apps and alerts you to anything that is using your cpu excessively. It might help unless it something that's draining consistently at a low level.

I'd have to agree that it doesn't sound like you have a problem. Battery life seems good.

Juice Plotter is another battery monitor that you might be interested in and its companion app Juice defender might help squeeze extra life out of your phone as it can switch off your 3G off unless needed.

Everything drains the battery. The screen is usually a big drain on the battery. GPS will drain it, wifi, internet usage, phone calls, etc.

If you got 2 days out of one charge, then you got good usage out of it. My phone is almost always tethered to power whenever it is available. Desk at work, Desk at home, Car charger.

On my device (running CyanogenMod 7), I can go to Settings -> Application -> Battery Usage.

My screen shuts off after 15 seconds and it is 75% of the battery consumer.