Like all things it has it's pro's and con's.
Basically net neutrality means that all content on the internet should be treated the same. Total equality for every single bit of data running through the pipes.
Taking that away means that providers can say MYST is not a priority and slow your speed because it isn't on one of their high priority lists. So you visit google.com and it's super fast, but you visit MYST and it's super slow.