MLB '06: The Show is definately worth it.
The season mode is far surperior to any other baseball sim season mode I have played before. There is basically no limitations, being able to set prices for seats, buy team buses and planes, control consessions at the game and even schedule team promotions such as "hat night" or "glove night".
The gameplay is basically the same as every other baseball sim, and if you are not used to the controls you'll adjust to them in no time.
The only downside in this game are the many glitches. A few times after the game is played and the player of the game is shown, the game freezes, and many times while pitching, the pitch selections freeze in which the only thing you can do is try and pick off the runner.
In conclusion, If you're looking for the overall better game between MLB 06: The Show and MLB 2k6, this is definately the one to choose. Better gameplay, many more features, and definately much better graphics.