But they can easily have a bad impact on your application at the program. All it takes is looking stupid or mean to 1 person to torpedo an application. Conversely, it will take a whole month of superstar to move your application substantially higher than your paperwork/interview would otherwise merit.
The rotations are expensive. You have to learn all new faces, places and systems. And presumably you go there because you think you will like it - if you do, so what, you already liked it. If you don't like it because you found out things you otherwise wouldn't, how do you know that program X's warts are worse than program Y where you didn't rotate.
I just don't see the benefit.