JTO,
You're right, it's not huge. As always, JF perfectly explains some key differences between old and new hovering challenges. That said, there are good reasons to be concerned when such a powerful engine's exhaust is only a few inches above the landing surface in the last second or two of touchdown, followed by a rapid engine deceleration and the aircraft moving away to ease thermal feedback from the [now rather warm] surface to ac tyres. So far, the Wasp trials have shown safe, repeatable and reliable STO and VL operations at work and are equally testing ship-air interaction at the highest sortie rate yet done at sea by the USMC with this jet. The UK are involved and learning in order to plan for future sea trials with QEC in 2018.
The USMC will be the first Service in the world to go to sea with a squadron of 5th Gen combat aircraft - we know they won't be fully mission capable in respect of SDD but they will have a tested and confirmed A-A and A-G capability employable from their own ships.