I bought one and absolutely love. My rifle has never seen a drop of lube and clean up is a snap. Every rifle from here on out will have an NiB coated BCG. WMD will coat your existing BCG for $100.
Is it needed? Absolutely not. Is it worth the money? Probably not but to me it certainly is. A $100 is not a ton of money. It's a little extra measure of reliability and makes cleaning faster. That's worth a $100 to me.