My first year with a 2166 (last year) I did not use it. It came with the machine, but not installed, so I just left it out. I farm all no-till; corn, soybeans and wheat. I was very happy with the results.
For me, it is more important to have the straw spread as even as possible, not necessarily shred to bits.
The knives on my chopper are pretty wore, so I will replace them this winter.

The knives on my chopper are pretty wore, so I will replace them this winter.