I must admit, I had never heard of A.J. before Criminal Minds. She will be missed!
If it was CBS' decision to let her go, I can't help but believe that the Network will come to regret their decision. If it was A.J.'s decision to move on with her career, while I wish she had not chosen to go, I wish her well.
In my opinion, Criminal Minds lost a big part of its heart when JJ walked into that elevator.