It's a hybrid of centralization and decentralization:
Redemption of gateway balances: centralized, possibility of default
Transfer of gateway balances between third parties: decentralized, cryptographically secure
Overall doesn't Ripple look more like a hybrid of decentralized and distributed?
However, it can have a significant affect on people who use gateways as a store of value. For that, you really want gateways that are insured. This is a great application for Bitcoins, IMO.
I see Bitcoin as the store of value of the future. If we want to store money, or send it anonymously (absolutely anonymous Bitcoin transactions are coming), we have Bitcoin.
If we want to send money all around the world to all sorts of legitimate businesses and individuals in a bunch of different currencies, we have Ripple.