Pros:

• when worn in your backpack, and when the backpack is worn properly, could act as armor?basically this is what armor is -- plates that are inserted into vests.
• if the shooter is aiming at you, could this be used as a shield?
  -- i went to the website and it says you can use it to defend yourself, so i guess so

Cons:

• how heavy is this thing? the website didn't list weight. based on my experience helping design armor wear for a past project, armor plates can be pretty heavy for the typical person.
  -- depending on how heavy it is, you might not be able to "run and defend yourself"