Getting there. Honestly, they blew up a ton of rockets in the 60's just trying to get them INTO space in the first place. I would think that this is infinitely harder.
In spite of the risk I would rather see this tried on land...landing on a moving/rocking platform is much more difficult. I know the plan is to do it eventually on land so I'm not sure why they are waiting...though the rockets blowing up on failure will make a NIMBY scenario now I think