John Gruber:

Here’s the test. Take some normal people, where by “normal” I mean people who have never heard of TechCrunch or Daring Fireball. Give them brand new still-in-the-box iPhone 4’s and HTC Evos. Now ask them to make a video call to one another. With the iPhone 4, they’re going to be able to do it. The only thing that’s technically confusing about FaceTime is that it only works via Wi-Fi (I think many people have little understanding of the difference between Wi-Fi and 3G data — at least insofar as why a feature would work over one but not the other).

Exactly, I call it the ‘Mom Test’ – as in if my Mom can figure it out with no help from me – then that makes it easy to use.