I've had the opposite, the ball bounced in and went out but the goal was conceded! It's nice if they have put it a little random, as it is in real life (until FIFA decides to use video technology).
About the "miastkes" of players, it's very nice how those are implemented, both for you and for the CPU players. Very nice because if you mistime an action, you can see the result in a very realistic way (even ridiculous sometimes, which is good and fun). But it's amazing how they've found the way to simlutae mistakes in the CPU players, something you can try to exploit to your advantage.
For instance, it's the first time in a football game that I will consistently play long balls just to find that defender error that gives me the chance.
PES tried something similar years ago, but due to the scripted nature of things and the reduced chance of decision of the player, it went all wrong. In PES, sometimes your players would just fail something without any reason and felt really odd. In Fifa, due to the "manualness" of things, and due also to the brilliant physics engine, it's satisfying to do errors.
Playing Human vs. human it's also a lot of fun when Maldini mistimes a header and you score, or when you mistime a volley. The amount of unpredictability in this game has totally blown me. I was expecting a lot less by EA, maybe that's a result of the persistant lack of evolution of PES in the last years, that makes us even happier with the huge ammount of evolution FIFA has achieved in only one year.
Oh, and yesterday I had the opponent Goalkeeper comint to my area in a corner. They headed the ball out and when I kicked from the keeper he was still running in the midfield to his goal. I managed to get a shot from halfline but it was Ashley Cole the one who shot and the ball went horribly wide. A very nice touch.