I just wanted to say that the first time I heard about this idea I thought it was dumb. The first thing you learn when you learn about space flight is that the only thing that matters is weight. The vast majority of the fuel in a rocket is there to push up the fuel that will push up the fuel that will actually push up the payload. So keeping fuel in the rocket to land it seems like a huge waste, but I was WRONG. It turns out that you can let a rocket fall through the atmosphere and because of drag, it doesn't actually get going that fast, so slowing it down from terminal velocity to zero miles per hour takes fuel, but not nearly as much fuel as I would have expected. What's more, the cost of the rocket, the engine, is a far bigger piece of the price than the fuel, making it even more worthwhile to try and reuse these things. Indeed, the refurbishment and reuse of engines may end up being the more difficult part of the process.

Anyway, I just wanted to say that I was WRONG, and that this is beautiful, and SpaceX is awesome.