These batteries do get better over time. I have owned several android phones since the HTC G1 was released and the battery life on the last 5 android devices (Since the Samsung Vibrant) has always improved over time. My Evo 4G was up to around 30 hours per charge.
Are you manually killing apps or using a third-party app manager? If you are, try to refrain from that practice, it's the fastest way to kill battery life. If you aren't using them, turn off or reduce background polling services (email checking, social networking updates, weather updates, etc.).
Finally, since this is a new device for you, you're probably doing what we all do when we get a new "toy", playing with it constantly. Battery life is directly proportionate to device use, this holds true for any battery-powered device, so the more you're using it the faster battery life decreases.