Dan - as per the review, a rotary aimed at those coming from the DJM/Xone type of 4 channel mixers.
Send/Return for me is key so I can start using my RMX500 again. My DB2 is great, but the effects are very very complicated and im not really utilising them as much as I should be. Whatever you say about DJMs, the effects sections have always been very user friendly and intuitive in a live environment. Same of the RMX/EFX units Pioneer made