Ripple is very difficult to understand and therefore is difficult to argument against it.
But what I understood it is centralized and not open source.
Another problem is that it needs gateways like exchanges by bitcoin and actually there only one gateway.
Without gateways to fiat you cannot transfer fiat money just Ripple.
So the problem which exists by bitcoin with exchanges by Ripple is even worse at the moment it is just hidden by the complexity of the system which is difficult to understand.
This is pretty much all true. But none of these things are fundamental about Ripple. It's just the difference between where we are and where we are going. You basically just summarized our priority list right now.
The XRP currency is somewhat similar to bitcoin, a fixed supply of coins that are owned by the company. The same deflationary characteristics only with a central issuer that hopes to earn money from seigniorage. So instead of individual speculators riding the deflation bubble, there is a single company dedicated to this, conjuring money out of thin air and playing the role of the central bank. I have to say the scheme is pretty sleazy and smart at the same time, but hardly revolutionary. If Ripple is successful there will be tremendous pressure from regulators to break or cripple it's anonymity and the company will have no choice but to comply. It's utterly irrelevant if the source is open, since the company owns the "central bank" keys, and there will be no reason to move to a different network with other keys where none of your money are valid anymore.
They way in which I understand it is that as soon as the server source code will be made open source, the whole network will completely become decentralized because everybody can run their own Ripple servers/nodes/gateways. OpenCoin does not have to do anything after that to keep Ripple running.
I dont know what you mean by 'central bank keys' though, I guess you are referring to the vast amounts of Ripples (XRP) that they will still be holding? Their stated pla is to distribute those over the course of the next years (decades?) to help solve the initial distribution problem. If at any point in time regulators would threaten to seize those assets (XRP), they could simply move them to an unknown address or distribute them all at once in a faucet like fashion as they have done in this forum already.