When I was on Android 1.5, my battery life was never as horrible as some other people have experienced. I could pretty easily get over 24 hours of battery life out of a single charge with moderate usage. After the Android 2.1 update, I will get between 24 hours and 48 hours of battery life with moderate to heavy usage of my Sprint HTC Hero. This includes: using the web browser, lots of texting, messing around on the Android Market, watching some YouTube or Flash videos and a few phone calls throughout that time period.
If I leave my phone alone or use it very lightly, I have no doubt I could squeeze nearly three days of life out of it on one charge. But, really, the point of this handset is to enjoy it.