I think it is worth it, especially if you can be careless with phones. I didn't buy it and was hoping I could have added it before phone shipped but that option isnt available.
That's another question I had ... for example with Apple Care; you can buy it and attach it to the iPhone 60 days out from day of purchase...so it doesn't have to be purchased at time of purchase. I wonder if Nexus Protect works the same way.