I've had my Desire for 4 weeks. The first week was so bad I almost returned it (I was getting 4 to 6 hours use between charges). Once I had basically turned everything off (sync, wifi, 3G, widgets, screen brightness) and stopped using the phone as a smartphone (no internet, games, multimedia) and just used it for texts the battery (unsurprisingly) lasted longer.
Despite what you may read here I have first hand experience with the iPhone4. It can last
at least 2 full days on one charge with wifi, 3G and regular use (internet, image capture, navigation and more).
Let me be clear: I am not an apple fan boy by any means. I bought the Desire because I absolutely love google. I am fully tapped into the google cloud (and have been for a while) and the ability to integrate my phone was (and is to some extent) absolutely fantastic.
If the Desire could be used at full whack for 2 days without a charge I would ignore the unforgivably poor multimedia capture and have no problem whatsoever keeping it as my primary device. Currently 2 days isn't possible just using the phone to text
and nothing else.
For those of us that want (or require) a truly mobile experience the
exceptionally poor battery life kills the desire dead in its tracks. Sad but true.