The fascinating thing about Ripple is it really exposes the critical flaw in the current banking and currency system.
I wondered why Ripple had to create their own credit unit for expressing loans. Then I finally realized: they could never have used BTC, precisely because BTC is non-reversible.
In our current system, banks can create and lend the very same thing that is on deposit in their vault. There is no separation between hard currency and credit. The complete non-suitability of BTC for credit makes this totally clear!
Ripple credits are subject to all the same problems as USD and all other currencies. Maybe the banking entity model is new, but most of the old problems remain and will appear in no time.
Reversible transactions, debt money, central banks, all of those cause problems.