A quote from this article by Guy Kawasaki about Steve Jobs:
This experience taught me that you should tell the truth and worry less about the consequences for three reasons:
1) Telling the truth is a test of your character and intelligence. You need strength to tell the truth and intelligence to recognize what is true.
2) People yearn for the truth—that is, telling people that their product is good just to be positive doesn’t help them improve it.
3) There’s only one truth, so it’s easier to be consistent if you’re honest. If you are dishonest, you have to keep track of what you said.