I've been wondering whether it's doable. By default it is mapped to "Enter" and RMB - which is fine if you're using mouse (and also familiar if you're Rhino user).
But it's not so cool if you're using MoI with graphics tablet - you either need to move your hand over to Enter or use one of those flimsy buttons on the pen (or use buttons on the side panel). I'd love to map it to "Space" key as it would allow me to confirm / launch last command without any extra hand movement.