As long as Ripple is closed source, it should be compared to Mt Gox, not the totality of all exchanges. Once it is open-sourced, it should be compared to the totality. For the former, it is no worse than Mt Gox, and for the latter it's substantially better. In other words, it holds great promise.

And what about Open Transactions? It doesn't have its own cryptocurrency, but allows you trade in all kinds of currencies, just like Ripple. And unlike Ripple it has already been open-sourced.