Well, now with the introduction of Siri, you can do the same thing. With Siri this feature becomes much more useful, as Siri can make more mistakes than you usually do – some of the times.
If Siri did not get what you said, just shake the phone and choose Undo Dictation. If the phone does not show the choices when you shake after a dictation to Siri, just shake harder. It needs a little vigour.
This work on the iPad and iPod as well.
By the way, if Siri is taking too long to respond showing you the three dots changing colors, you have two choices. You can hit backspace to kill that command and try again. You also have the choice to continue typing while the dots try to complete your previous command in the background. You don’t have to wait for Siri to complete and respond to the previous command.