Originally Posted by KRosh

You still manage your server - This is just the Name Server. You will be able to move hosting, add subdomains, make NS changes on the fly and in minutes, rather than the typical 24-72 hour propagation.
It can increase the speed of your site, and If one nameserver goes offline or an area of the internet temporarily fail, there will be several other name servers in other geographical locations to fill the gap and provide nameservices for your domain.