Miserable. We stayed at the Vatnsholt Inn for a few days. We paid about 110 euros/night. We chose it based on online reviews. Major disappointment! The online photos, descriptions, and reviews were very misleading, in our opinion. The "hotel" is a long prefab shed outbuilding on the "farm," cheaply walled off into a row of mean rooms. The rooms are wretched, tiny, shabby construction, bad linoleum floors, unusable bathroom. Rooms smelled of bad plumbing and were noisy -- each time someone entered the room shed, it was loud and shook the entire building. No phones or wireless access. Bedding was low-quality but newish synthetic comforter and pillow. Room was somewhat clean -- there was mildew and some filth in the bathroom, a few human hairs on the sheets/pillows, etc. For showers, we ended up driving to a different town and used their (very nice) public showers/bathhouse.
The location isn't good either -- deep in the boggy and depressing area below Rte 1. The nearest town Selfoss is down-and-out. The farm was not maintained well, in my opinion. Livestock droppings around the hotel buildings weren't shoveled up during our stay. Dung flies got into our room, and attacked our face and eyes at night.
The common/eating/restaurant area is a huge cold room in a prefab outbuilding, half of which is a walled-off dark are where the livestock live. Internet access often didn't work. Breakfast was a lower quality but complete Scandinavian buffet. Nothing was "homemade" -- coffee and "juice" came from a vending machine, everything else was gas-station quality storebought. The same food came out every day until it was used up.
The other guests seemed miserable, and no one socialized with each other. The people working there were friendly enough, but didn't help much with advice about the area. The farm animals were friendly, some sadly flea-ridden dogs, and a surprising menagerie of expensive "status" pets (English Bulldog, Chinese Cresteds).
All in all, Vatnsholt felt like a tourist trap. The reality was a shock, compared to online reviews and touts. We won't stay here again -- when we return to Iceland, we'll stay at an Edda (school dorms converted to hotels for summer) which at least are built for human habitation. I'm sorry to say this but my advice is, stay somewhere else.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC