You are forced to have a html email that is centered on the page.

If you want to achieve a look that resembles a standard email (i.e. pure plain text that's not wrapped in a div, given a max-width, and centered), as you would get from a friend, this is not possible.

For certain campaigns this is desirable. If I adopt a daily, talking to friends approach, clearly commercial styled emails don't get the click through rates a simple text-only email can achieve.