Factorio in Minecraft is a great idea and another great way to attempt automation in bukkit.
Machines work well, and I love the glass blocks that show whether or not where you're looking is a valid location to place your block. Only issue I really had is the pickaxe, nor anything else for that matter, could break any of the structures I placed. And for the structures that placed new blocks rather than replacing them, I had to click twice to place them.
Unfortunately the originality rating is a bit low due to the fact that it is based off another game; Factorio.