Hi there!
Not sure if it’s just me, but I very love the scrub playback. And while I’m trained pressing “Alt” first and then adding “Space”, I usually let go both keys at the same time. Often this makes the “Alt”-Key getting released a few ms before the “Space”-bar, resulting in playing back the score. Combined with NotePerformers delay this gets very time consuming very quickly, when I use scrub a lot. Is it just me, not being able to use shortcuts?
Otherwise I would propose a lock for the spacebar, after the shortcut was used. This is how other shortcuts usually seem to work. (Cmd + V does not write “v”, when I let got Cmd first)
Anyway, so glad this feature arrived, makes things so much easier! 
Thank you!