Generally, the two biggest problems with spiros right now are:
If you add a node between two nodes, you don't get a node on the "line" between the two nodes you are inserting between, but somewhere. (Which changes like everything.)
Having a path, you can't switch between a spiro and a bezier view. (Deleting the spiro effect changes everything you did and, while you just temporarily want what you get with Ctrl+Shift+C)
(And having a node selected it's not possible to select the next or previous node with the keyboard and then to insert a node with the keyboard.)
Generally, the two biggest problems with spiros right now are:
If you add a node between two nodes, you don't get a node on the "line" between the two nodes you are inserting between, but somewhere. (Which changes like everything.)
Having a path, you can't switch between a spiro and a bezier view. (Deleting the spiro effect changes everything you did and, while you just temporarily want what you get with Ctrl+Shift+C)
(And having a node selected it's not possible to select the next or previous node with the keyboard and then to insert a node with the keyboard.)