The new arrow functionality in Balsamiq if just great! Love the improved control over curved and lined arrows.
I use “line” arrows a lot to add comments to my mockups, and at the moment it’s a real pain in the ass to create an arrow that has 90 degrees angle. It would be great if you could just keep Shift key pressed while dragging and arrow joint, and the joint would snap to its neighbour joint’s position. That would make creating dead-straight and 90 degree arrows way easier, as these days all my arrows are at some 86 degrees.
Here’s a typical way for me to use them arrows: