I don't doubt that it would work fine in plasterboard - don't forget that oscillating saws were originally invented (and continue to be used for) cutting plaster casts in hospital plaster rooms, and cutting skulls in hospital operating theatres and autopsy rooms - for all of which purposes the advantage is the low risk of damaging underlying tissues (as compared with a rotating, rather than oscillating, blade). Plasterboard is therfore close to being the 'ideal' material to cut with such a tool..Purely for plasterboard though, it wouldn't have a hope in hell with ply or MDF, because it does really just chew it's way through, rather than cutting its way through.
However, I'm confused about the way this discussion has evolved - I thought we were talking about making (fairly small) holes through (hard) wooden joists, not cutting (relatively large) holes in plasterboard??
Kind Regards, John