Ideally they reach zero velocity the instant the legs touch the ground. There was only one hard landing (that didn't result in a fireball) so far, and the legs

Ideally they reach zero velocity the instant the legs touch the ground. There was only one hard landing (that didn't result in a fireball) so far, and the legs are designed to take the remaining speed (they are replaced anyway and not reused). They also have no other option. Even one engine at lowest throttle (70 %) is powerful enough to lift the almost empty booster again, so they cannot hover (which would make things a bit easier, at the expense of needing more fuel).