...I can assure you that Ripple is not a scam, but I can't guarantee that it isn't a threat to Bitcoin.
While still completely controlled and closed, I doubt it constitutes a threat to bitcoin. Mining isn't such a 'waste' as the Ripple creators claim that we need to give an organization control of issuing currency. We already had that with fiat. No one should wield such power.
Open Transactions + Bitmessage + Bitcoin seems the holy trinity to me.