Elon is saying that the mission was completely successful, but they lost the first stage. First relight to gentle the entry was successful, but the second one to come into the ocean resulted in an exceedance of attitude control authority for roll. Centrifuged propellant shut down engine prematurely. But they’re getting all the pieces, so they’ll be able to figure out how to fix for next time.
[Update a few minutes later]
First and second stage engines performed better than predicted. Pad also worked well.
[Update a few minutes later]
Second stage shut down prematurely, but didn’t affect mission, apparently. They know why and will fix for next flight. Next two flights won’t attempt first-stage recovery, in order to maximize payload for customers. [All via @Jeff_Foust]
Next recovery attempt will be on CRS-3. Vehicle may also have landing legs (implies attempt at flyback to land, not ocean — today’s flight must have inspired confidence).
[Update a while later]
I mistyped above. The second stage didn’t shut down prematurely, it had a problem with restart. But I think it was just a test of the vehicle, and didn’t affect the primary mission.