So looking forward to this! Two things I've thought of while using Sib 6 a lot recently that could be improved...when you add grace notes to more than one voice on the same stave it does crazy things with note spacing that just don't line up. You can change them manually to something that looks reasonable then you go to a part and its messed up again.

Also, could the beam over rests function be linked with time signature like beam groupings are in Sib? Sib 6 has the overall option 'beam over rests=on/off' with no option to change mid score.

Regardless, please keep up the great work and keep us posted!
Cheers!