Have you ever sent a beta version of your game to a friend and asking her to play it? Have she said, "fun game, here's some constructive critisism, keep up the good work"? What does she mean with "fun game"? Well, what I have learned is that your friends will be friends, so they can't be trusted
What you should look for, in my experience, are the magic words, "hey, I played your game
again last night". If your friend has double-clicked your game's icon without you asking for it, then you have a winner! If your friend never does that, but only plays the game every time you increase the version number, then you should probably re-think your game design (assuming that your friend is a part of the potential target audience).
Of course, in linear or story-based games, it's more important to see if your friends play it all the way to the end than if they play it many times. My point is that you should pay more attention to what your friends
do rather than what they
say.
Your thoughts?