Do you mean turning off just Mu-Mimo, or also inmplicit and explicit beam forming (since they are three different options in the professional menu)?
We were specifically discussing the uselessness of MU-MIMO. Beamforming works, but it can also introduce compatibility issues depending on your clients.
Merlin, are you going to be integrating on top of that newer code base, or wait until the dust settles a bit.
I can't answer that until I've actually seen the source code, which is not available yet.