[verytrivial]

I can't find the reference, but I remember reading that the landing is complicated by the fact that even at minimum thrust, with the tanks nearly empty, the ship is so light that even with a single engine, it would accelerate back up after hitting zero velocity. So if the engines are restarted too early etc. it could "miss" the ground!

(If someone can confirm/deny this? I'm seeing approx 28T dry mass, thrust per engine of 66T and min thrust of 70%, but that dated guess work from http://space.stackexchange.com/q/4466/ )