I thought this would be a great idea since there are no parallel walls.
But it is roughly approaching a "round" floorplan. And I learned from
people that a concave "round shape" is terrible for a room.

So would you give this shape a thumbs-up or thumbs-down?
(I'm building an iso-booth this week).

With the right acoustical treatment, I have never had problems with any
room, no matter what the size or shape.