I use a Google Nexus, almost equivalent to the Desire, and I can recognize the battery drain. However, after a few weeks, the phone easily holds a day - probably because "moderate; use" is really "let's see what this device can do; use".
Also, some apps are written badly and consume a lot of power when in the background. If you are experimenting a lot with your phone, chances are big that you have installed one of these. There are two solutions:
1) Uninstall the bad apps.
2) Use a tool, like task killer, which can kill the bad apps when the screen turns off.
Additionally, if you are always online, and have enabled wifi, it will consume power. Quick solution: put a wifi on/off widget on your front screen, and keep wifi off under normal use.