I went to Komkommertijd twice over Easter weekend and thoroughly enjoyed the food. It's an all-you-can-eat buffet, and you pay when you're leaving. The dishes were all vegetable based and there's soup, hot dishes, a cold salad bar and dessert (one cake, plus fruit). Everything was fresh and delicious, with the exception of the soup which was a little bland.
Our only complaints were that we couldn't reserve via email, only by phone (which is pricey from the UK), and it was absolutely packed both times we went, so booking really is necessary. And we asked for tap water, but were told we could only have a glass if we ordered another drink first. I've never encountered that policy before and thought it was very poor.
Cons: No tap water, Difficult to book