First, let's set some ground rules. I am not a person who spends six hours a day streaming video over 4G. My typical daily usage includes about 20-30 minutes of phone calls, lots of checking of my Outlook email and Calendar plus sending an email or two, a bit of messaging and reading about 15 minutes of news. With all this I don't think that I am too untypical of many business users.
Under the above scenario I have found that my EVO will run all day without issue and have some left for the next day as well. I typically charge my smartphones daily so I don't often run a battery into the ground. The EVO has a pretty large battery (1500 Ma) to go along with its many features and large screen. For everyday use, I would classify the EVO as slightly better than most other smartphones I have used and certainly not worse. My negative dividing line on battery life is if I have to make a mid-day charging session. I have found it not necessary under my operating conditions with the EVO.
Now, this does not mean that I will never stream video, take HD movies or turn on 4G but that will undoubtedly come later and I will see how things fare then.