The main problem I've encountered with the handy dandy hinge rotators is that the "center" is not actually on the point of rotation for the hinge itself. In essence, you can't build a gear door that's built open and expect it to close properly on the first try. Regular rotators work for this, but they wobble more, especially when 2 rotators are stacked to create a 2 dimensional rotation. This would definitely aid the process of building gear doors, airbrakes, and other rotatey bits as it would allow smooth and accurate nudging and rotating.