Instant reply doesn't belong in baseball. Baseball is already a slow game, instant reply would just make it worse. Incidents like this is what makes baseball great as it brings the controversy to the public to decide and fuels the fans.
This wouldn't even be an issue if the Angels catcher would have just put a tag on Pierzynski like any good catcher would. When you don't do what your supposed to and the batter is a catcher also, he is going to take advantage of it and hope for the best call.
And yes I am a White Sox fan and think that the ball was caught when looking at it from dead on.
