I want it (and for the same reason I wanted a roof on the new stadium).
I think it's the only way to be fair to the players and the fans.
But I think football has it right: the officials are a part of the game, and they are the final authority. But you can challenge authority on occasion.
Give each manager one challenge each game (not on balls and strikes), let the official scorer (who's probably watching a few replays already) make a decision. No more overturns, no more playing under protest. If you challenge in the third inning on a questionable home run, it means you can't challenge in the ninth even though you're sure that your guy beat out the inning ending double play.