I'm mixed. It's too blatant a plot device, and a lot of its importance tends to be at the expense of Zoro's other swords, and Zoro himself at times. He's a three swords user, not a one sword user. However, I like it for expanding the lore and premise around swords in the verse, and it forced Zoro to confront some of the demons that plagued him, such as an uncertainty in his own abilities.