Sounds like you got a bad Sprint rep try someone else. My Battery lasts me all day even with medium to heavy use. If I turn on my Intrepid and keep it on it will run streaming video for about 5 hours without shutting off. If I run bluetooth with some calls, a few email, Push mail running, and light web surfing I get through the day with ease.
I leave mine on all the time, I don't really use the internet much, but I do have it checking email, and keeping my weather app up to date, I have to charge it every couple of days, I think the battery is great, compared to the HTC touch.
One thing that I read somewhere is to remove the SIMM card to improve battery life. Apparently, this cuts down on your phone's searching for networks that do not exist in the US (depending on who your vendor is - mine is Sprint, which does not need a SIMM card to function).