Looking at those who are in favor of net neutrality, it appears like any other pro-regulation base of support. The arguments lack a number of important factors.
First, if networks begin charging extra for better bandwidth, what kind of charge would it be? Such concerns might be warranted if there is a high, flat charge. However, a low, flat charge or costs being directly proportional to traffic should not be too hard for a website to shoulder. And is there really any realistic concern over such a proposition? Over the past decade, the internet has grown at leaps and bounds, far faster and far more widely used than any other technology known to man. Competition has been healthy among many network providers, as the loading speed of many websites has increased dramatically. Such costs could have been incurred a long ways back, and instead, all customers have found that "big business" has given everyone more for their money, not bigger bills.
Then, there is the little problem of government regulation. When a government regulates, that means there are LESS choices, not more. First, if networks do choose to add costs for better bandwidth, this opens up an opportunity for competition; people will be more likely to use services which aid them more, and the companies that do choose to add these costs may have to remove them if they lose too much business. If one company provides bad service, you can always switch to another; if a government provides bad service, switching is a bit of a challenge.
What's worse, the government may choose to tax and regulate web content. Certainly there is some objectionable content online, but where is the line drawn? Will political material (such as, oh say, The Red Stater) be subject to regulation as it might be considered "endorsement hate speech" when speaking of terrorism? Would the status of a blogger as press be challenged, taking away our very first amendment rights? Internet regulation is one step away from regulating our spoken conversations. The government is involved enough in my life, I do not need them telling me I cannot give my thoughts on the most recent SCOTUS decision.
Liberals and many computer users will probably say that Republicans and crossover-voting Democrats in the House were pandering to big business; on the contrary, they have served the American people by upholding our Constitution and the Bill of Rights.