My girlfriend and I stayed with Cleiton and Koen over Easter break and we had a fantastic time, thanks largely in part to their hospitality, helpfulness, and the excellence of the room we were given. As hosts, Cleiton and Koen went above and beyond the call of what can be expected of an average host. They cared very much that we were comfortable and also secure in our travel plans (such as printing out tickets and boarding passes for us). They were both wonderfully friendly, hospitable, and attentive, but neither was intrusive or overly social, so at all times we felt perfectly fine reaching out to them to ask questions or request help with something.
I personally can't say enough good things about Cleiton and Koen. A huge part of the success of our trip we owe to them. My only advice to the traveler(s) who will book with them next is to buy and use bottled water while you are there, as the tap water in the apartment is quite sour, something Cleiton let us know upon arrival. Bottled water is very cheap so that's not a problem but you should make plans to buy some prior to or during your stay.