I got to try the new HvH metro link a couple of weeks back, en route from London to Hamburg. All very modern and swish, but a bit disappointing compared to the old days when there were "proper" railway carriages sitting there next to the boat to take you, direct, half way across Europe...
Also, waiting a while to set off - on one of those old long-distance connections - was fine; but standing on a windy platform for half an hour (it was a weekend, and I'd just missed a metro, which is only twice hourly at weekends) felt a bit of a let-down.
But at least the through sail-rail ticket from London was fine for the metro as well as for the subsequent regular Dutch trains.