Oceanic is my name for a plan for an intermicronational payment system based on the Ripple monetary system by Ryan Fugger.
To users who are already part of an economy and only need banking functionality, it will appear as a web bank much like ShireBank, though with a few frills you can ignore. Once you have set up an account (for Shirithians, I expect this will involve a single password change where you get your new password emailed to you) you will be able to just click on pay and pay people, and you will be able to see payments made to and by you, etc.. You *won't* be able to see other people's account balances - this will be private in Oceanic. In essence, life for you will be pretty much the same as it was before. (a state will, however, be able to see how much state-issued money each of its citizens has, simply by looking at its own account)
To people interested in national economic policy such as Andreas and me, well, there's a paper on the Ripple monetary system for us to read: Money as IOUs in Social Trust Networks. They'll have a chance to set exchange rates (the setting is global so the rates will probably be negotiated on a national level instead of determined by the market or such), to watch trade balances (at least of the payments that get routed through the central systems), and regulate the part of international trade where the payments go through central accounts they'll set up. In essence, the people involved with your money will have more tools to make it do things.
To people who don't like what they read in the last paragraph and would like to stay as far as they can from centralised economic regulation - Ripple does not even have a concept of nation, and it will allow you to make credit relationships with whomever you feel you can trust. Of course, this could mean that life's getting interesting - since payments can be routed through any path of credit and credit means what you agree for it to mean with the other guy, you could wake up one day to find out that two people (you don't get to know who - it's part of the system's privacy) have made a trade somewhere in the microworld and now you owe one guy a story and another one owes you a picture. In other words, if you want to do fun things with it, you'll find it ridiculously flexible.
To people in nations that aren't initial signatories who might want to participate in the economy - assuming the money in it does manage to get valuable enough to be worth it - there will be a chance to join in. By the nature of Ripple a single person can act as an economic "gateway" to another that's off the official grid as long as there's mutual trust. If there is actual economic value to be found inside Oceanic, it will be able to spread incrementally, and subsume national economies. This is a pretty significant distinction to the SCUCT where only nations can join.
To summarise the benefits: There will be actual currencies with exchange rates; your account information will be private (I'm somewhat convinced most people prefer it this way); the system will be flexible for the people who want to play with it but work just like before for the people who don't; and it can be adopted more incrementally than the SCUCT.
To summarise reasons you might not want it: If you use the flexibility to make life complicated for yourself, well, life will be more complicated: You could find that you don't have a single account balance anymore, or that you have been used as part of a payment path and have now developed two new debts, one to pay and one to collect. But that's only if you go through the effort to complicate your life; Nations won't be able to enforce regulation very well as your privacy will be protected from micronational jurisdictions; and it *will* take me a while to set everything up to work really smoothly.
There will be more later, much more. I'll just have to actually host this thing first.