I would absolutely not want a game determined either way by one of those split second plays at 2b that can only be spotted going frame by frame. I'm not against replay, I think it is especially valuable for home runs and fair/foul balls. Personally, I would only allow challenges if called for within 5 seconds or if umps wanted another look themselves. Too much standing around, not even great outcomes when used. For me, it is about fairness, not perfection. And it is not like computer zones won't have problems, there is enough of an error margin that will exist that it is not especially clear it will be that much more accurate overall. And on a final point, while I do like technology, I also like to occasionally get away from it. Baseball is still a sport, played outdoors. Waiting for a red/green light after every pitch would not enhance the experience for me, no matter how "accurate" it claimed to be. There would be unintended consequences to this that really aren't being thought through enough. Replay right now is not a finely tuned machine, and the fixes aren't obvious either.