Net Neutrality is a pretty simple concept—the infrastructure of the internet belongs equally to anyone willing to pay for access to it and the basic rules of “free speech†apply. 
You might pay for a faster connection or a higher level of service but once you’re connected you can send and receive packets to and from anywhere. In the US, cable companies and telcos are beginning to argue that the ability to “tier†the service makes more sense, and from their point of view it certainly does. For example, if you could retard the delivery of VoIP packets wouldn’t that tend to help SBC’s telephone business? And why, after all, should Comcast provide the infrastructure to deliver IPTV or BitTorrent packets instead of making sure your media comes from Comcast servers?
The forthcoming Senate debate on S2686 which rewrites the 1934 telecommunications act will probably decide the issue. Ted Stevens (R-Alaska) is sponsor of the new legislation and he’s firmly against the idea of adding net neutrality provisions to his bill. Of course, if you give a listen to his explanation of how the internet works (“it’s a series of tubes”), you realize he probably thinks “net neutrality” has something to do with staying out of disputes over international fishing rights.