Well apparently its not if you ask a lot of goal keepers. The ball is suppose to be highly accurate, but a lot of goal keepers are complaining about the ball moving a lot while in the air. I can speak from personal experience that a lot of keepers tend to react fairly early to where they think the ball is going, that is why you sometimes see keepers miss stopping the ball by quite a bit.
This is also the reason why a lot of players focus a lot on bending the ball (bend it like beckham,) because as the ball travels through the air it will gradually start changing direction. From what I've read the ball is even taking weird bounces after it hits the ground, so much so that some keepers have started training with regular (american) footballs that obviously bounce weird when it hits the ground.
So far the scoring seems to be down from past world cups. It does seem like each world cup keeps having less and less goals scored. Everybody was saying that the 2006 WC only averaged like 2.3 goals per game which was the lowest behind Italy in 1990, wheich was only 2.2. Some people would blame the ball, but I believe that it has a lot to also do with the keepers making great stops.