My desire lasts around 2 days with moderate usage. But on a good day (read: many boring moments), it's completely depleted by the end of the day. My biggest battery drainer is whatsapp, if I uninstall the app my battery will last a LOT longer.
If i really need my phone to last for a long time (when Im on a big trip or on a festival) I always use JuiceDefender with a very strict setting. This is a big help, but not for everyday use