I recently bought this game after never having played a MLB The Show game.
I have played MLB 2K games before they stopped making them, but they are a bug-filled joke compared to this game.
The graphics (models, textures, lighting and shaders) are pretty exceptional, and the game is easy to play. The modest amount of jokebox music in the game is of good selection. The AI is exceptional as to be expected - just like in real life, throw a ball anywhere toward the middle at David Ortiz too much, and he will knock it out of the park.
My advice is, give this a rental if you like baseball a little, give it a buy if you're pretty into the sport.