I tried to go to De Hoop just over 5 years ago, and while J and I (with J's wife K) managed to get to Bedasdorp; for various reasons we didn't actually manage to make it to De Hoop.
From all accounts from the staff, De Hoop is not well known - and many of the patrons are actually regulars. One lady was staying for 7 days, and this was her 4th consecutive visit over Christmas. She was also excited that she had already secured a spot for 2016.
And De Hoop is a gem - there is off course the unique landscape and environment, but it is the absolutely amazing staff that makes De Hoop such an attractive destination. Most are locals - they have grown up around the area; and some can trace multiple generations in the area. They are very friendly and very approachable - hospitality at its best. And many of the waiters/hosts double up as guides with amazing knowledge of the environment. There seems to be a concerted effort in skills training based on the stories of their experiences but as one guide mentioned - it is not only the knowledge; it is how well they can interact with the guests that really define how successful they are.
Broadly, De Hoop has three environments - fynbos hills, the coast and a "vlei" (translates to a marsh, but more lake/estuary). There is not much variety in terms of large animal life in the fynbos - lots of eland and bontebok, with some cape mountain zebra and ostriches. De Hoop is a marine sanctuary, and so whale season leads to frequent sightings of whales and their calves; and the rock pools are teaming with actuatic life. The bird life is amazing - blue cranes, fish eagles and oyster catchers - there is a lot of variety to be seen (apparently 260 species in total).
The dunes are dramatic, the beaches are pristine; and the staff are very hospitable. I do want to come back for the whale trail hiking trail; or perhaps for the whale season. While I doubt I will make it an annual pilgrimage, I can certainly see what the attraction is.