I view net neutrality as thus: no website, piece of content, game, etc., gets VIP treatment by ISPs. All content on the Internet is viewed as equal in terms of how an ISP lets you access it. This does not include the speed of access that you, the client of the ISP, pay for. I like the comparison that Henry Blodget made between package delivery and ISPs (http://www.sfgate.com/cgi-bin/article.cgi?f=/g/a/2010/12/21/businessinsider-all-bits-are-not-created-equal-and-you-net-neutrality-zealots-are-just-looking-out-for-your-own-self-interest-2010-12.DTL#ixzz19wK8F3RL). Everyone has a basic, cheapest version of package delivery speed that they get access to. If someone wants their package to arrive faster than this basic speed then they pay extra money for it. This is currently how ISPs work. If you want faster Internet access you pay more than the person who doesn't want or need that much speed. This also applies to bandwidth even though providers have been making a lot of money charging for large amounts of bandwidth that people couldn't come close to using up until recently.
I believe that net neutrality is important to have. If we think about it like businesses along a road, then the road is the Internet and the businesses the content. The road itself doesn't discriminate against any business and ISPs should not discriminate against content. Sure, parking spaces and land design might give one business an advantage over the other, but that advantage is being paid for with money. This relates to the Internet access and bandwidth for websites and such that a business might pay for.
If we lose net neutrality (and wireless access is getting closer to it) then we lose a huge part of what the Internet is: freedom. With our Internet access so slow and fractured compared with the rest of the world we as a country can't afford to slow down any further. Would small websites be able to function at all if they didn't pay so their patrons could have decent access? Would the price be prohibitively large? Who decides what a good price is? I'm sure most ISPs would balance out their prices with the competition and denying access to content would certainly make them less popular, but they're still businesses: it's all about the money.