We spend 3 nights in the hotel and had a lovely stay.
The hotel staff is very friendly and really supportive. From the reception to the staff at the bar, the restaurant, lounge and the housekeeping staff, they were always friendly and I really felt we could ask them anything. Quick example: we were missing 1 type of pillow in the room, asked reception and 30 mins later the housekeeping staff brought the pillow to the room. All with a big smile.
The food in the restaurant and the lounge is good and the prices are what is to be expected from a hotel restaurant/ lounge. (3-course dinner with drinks was €150 for 2).
We loved the fact that in the morning there was a small paper on the breakfast table highlighting an excursion you could do. We did 2 of those and they were really nice (visit of the Arbotreum and a bike tour).
Now, we were unlucky with the weather, but that is nothing the hotel can change, so we also enjoyed the pool (it is small, but nice to take a dip) and their sauna area (which we really liked).
All in all, we had a lovely time and we really appreciate how friendly the staff was and we felt taken care of.
Price / Quality, we recommend De wilmersberg.

We spent (unfortunately) only one night at De Wilmersberg. It was a perfect beautiful spot in the Dutch countryside. We loved riding bikes in the area and especially the walking paths around the property. In the evening we had an excellent dinner at the restaurant. We would love to come back some time for a longer period. The area is just beautiful for exploring.

Perfectly situated close to the Dutch/German border, and thankfully only 2 hrs from Amsterdam. This hotel is a total gem! Beautiful gardens, birdsong to wake up to, a stunning restaurant (both dinner and breakfast are exceptional), calm, and some super staff running a ship-shape hotel. The spa/swimming area is great (apart from the slightly awkward nudity if you are not Dutch/German), and for the fairly good price you get an absolute top notch stay. Will gladly return next time I am on a business trip in Netherlands, and need somewhere to unwind and be refreshed!