The Vatnajökull National Park area is a bit unusual, as it includes the Jökulsargljufur National Park, which has no borders to the rest of the park, creating a second location for the site. Having just visited this exclave, I can highly recommend it. It features some of the most spectacular scenery in a country overflowing with great landscapes. The glacier-fed river Jökulsa a Fjöllum (which orginates a long way down south in the main park area) is cutting through a landscape formed by raw volcanic rock. It creates a large canyon and tumbles down a series of waterfalls, including the mighty Dettifoss waterfall. It's a gripping display of raw elementary powers, with hardly any plant life or greenery in sight. Getting there is not too tough if you have a car, although the east side road is a bit rough (though probably a bit more rewarding). No 4x4 is needed, at least in summer. However, getting there as a day trip from Reykyavik is definitely out of the question. Most people do it as part of an Iceland round trip on the ring road 1, where the 2-3 hour detour is certainly worth it. Visiting in early autumn, there was no lack of tourists, but the large scale landscape could cope with it pretty well. Further north lies the Asbyrgi canyon, which is more fertile but less spectacular, but still highly enjoyable.
For the Skaftafell section in the south, I had good luck with the Jökulsarlon glacier lagoon, as there were lots of colorful icebergs floating right next to the car park, with a boat ride not really needed. There were lots of clouds and fog in the higher glacier regions, though, so the whole travel experience here relies a good bit on luck.
All in all, the Vatnajökull National Park is so large and so full of marvelous landscapes that a WHS designation seems quite deserved. Iceland has so far no natural WHS that covers its amazing landscape, so it's about time.
Visited in September 2018.
Importance 3/5 Beauty 5/5 Uniqueness 5/5 Environment 4/5 Experience 5/5