I stayed at the Sheraton Iguazu Hotel and Spa in Iguazu Falls, Argentina. While the hotel is the only one in the actual National Park and closest in proximity to the actual Falls area, there are other options but none that were close to the park. My experience at this hotel and it's customer service were atrocious. Upon checking in on a prepaid reservation that I had made many months ago, and specifically at a rate for three adults (using Kayak.com and through Travelocity) they refused to honor that rate and charged me approximately $170 US Dollars (1,000 Argentine Pesos) for the extra person even though the confirmation that I had in hand and showed them specifically noted that the rate was for 3 adults). They refused to budge from their position that the extra rate applied, refused to allow me to speak with a manager unless I could stay until later in the morning of departure (which would have meant missing my flight), refused to try and contact a manager or their reservation department when I complained about the charge at check in, and were exceptionally rude and condescending to me and the other members of my travel party- stating that "... well that's your problem then isn't it?" when I explained that the reservation confirmation specifically showed a 3 adult rate and that I could not miss a flight waiting for a manager to show up.
So beware- while a comfortable accommodation and the only one close to the spectacular falls area, they have terrible customer service, overcharge and do not even consider the customer's viewpoint, and are exceptionally unresponsive and outright disrespectful.
Otherwise the hotel was comfortable although somewhat run down,pool area was filthy, entrance exterior was in some stage of renovation and very poor condition.