At the beginning of the game I hated the shield durability, especially when my first wooden shield broke to an octorok in Faron. But now I really like the system. I think it adds a little bit more depth in the game play which I enjoy. I like the fact that there are different shields for varying purposes. Like the metal shield is stronger but is highly affected by electricity or that the wooden shield is low in durability and is destroyed by fire. I haven't got that far into the game so I haven't got the divine or Hylian shield yet. I think that having the different shields and the shield meter is a great idea. The shield meter might also be there to add to the challenge and to the upgrade system, because really if your shield was unbreakable at the beginning of the game, you would have no reason to upgrade it. As for the challenge, I use my shield a lot and that means it takes a beating, so when it breaks I am a little bit screwed, so that adds to the challenge at least for me.