Well, this is certainly a change for the better. With the new use of technology, many more (but still not all) "boundary calls" will be made correctly. So no more incidents like what happened to Delgado or ARod will occur. Of course there will be times when the umpires will feel confident that they saw the flight of the ball correctly, regardless of whether they actually did. But on the ones where the blues either don't see the play or aren't sure of the call, the correct call will be safe. On one hand it is a sad goodbye to wins caused by fortune (although there are still plenty of non-boundary calls to change the tide of the game). But looking on the bright side, no longer will batters be robbed of home runs nor pitchers charged with them unnecessarily. I think that this is a good choice, as tennis adopted the use of instant reply for serves and other borderline shots. And football has had replay for a while, which has enhanced the viewing experience. As MLB has predicted that the whole process from the time instant replay is called upon the be 2.5 minutes. I have to say that if it gets any longer than this amount of time, the pitchers will start to stiffen up, changing the course of play. Other than the possible delay of game, however, I see no possible downsides to instant replay.