Instant Replay In Baseball?

Should there be Instant Replay in baseball? Some say no, just because they want to keep baseball the way it has been for a hundred years. Then, there are the "radicals" (that really don't seem so radical), who are for the instant replay. The "purists" or anti-replay, say that it will take too long, and will slow down the already slow-paced game. But do people forget that after a questionable call, the manager comes out and yells at the umpire, wasting time when the call is never going to be reversed anyways. If anything, it would only help. Just like when baseball added four umpires during the regular season and six during the playoffs. We shouldn't have added those just because we didn't have them before? How does that make sense? How would we ever progress and make the game better? If we have the tools to make the calls more accurate, to make the game better, why not use them? It seems like the MLB is close to instating some sort of replay. Some minor league teams have had instant replay tested, and it seemed to work fine. Hopefully it will go into full effect and start fixing questionable calls soon.