Zagg's Invisible Shield is awesome--I have one on my LG Vu. I considered getting one for my NC, but I liked the anti-glare screen protector B&N was offering and I didn't want to wait for one from Zagg to come in the mail.
Invisible Shield has pros and cons, IMO. Pro is certainly the near-indestructibility of the screen protector. Con (for me, at least) is the somewhat rubberized texture. The texture is great on my phone, it helps with gripping and such, but for the NC, I like the B&N screen protector's smooth surface, and the anti-glare is really nice.
With the B&N anti-glare screen protector, you get two. So when one wears out, you apply the other or take it in to B&N and they'll remove the old and apply the new for you. Otherwise, Invisible Shield has a lifetime warranty on it, but you need Retail Location access (correct me if I'm wrong) for warranty/product replacement.
In the States (California, at least), I know for sure there is a retail location in Palmdale, CA, at the mall, and I know Best Buy sells Invisible Shield products (don't know if they cover the warranty/replacement--probably not). Otherwise, sign up for emails from Zagg, they have 50% off sales/coupons for the website all the time.