It can make something an artifact permanently, and it plays into any deck's framework where you want to en-artifact your stuff to enhance them with cards like Darksteel Forge or Padeem, Consul of Innovation
Like Tome of the Infinite, I expect players will try it, if not in the main deck then in the sideboard, but I'm unsure if it will stick around
Gollum, Patient Plotter as commander of a sacrifice deck is probably the very fastest way to finish the Rings dungeon-like levels
Just as Burn struggles to win with Lightning Bolt alone, you need a cheap creature that generates value over time in order to really maximize your mill count, and the Crab is simply best-in-class
They leave enough space for the printing of numbers, symbols, and artwork