Sheraton is the only hotel within Iguazu Park which makes it entirely worth it to stay here. You can see the falls from the hotel which is pretty amazing. The daily breakfast is pretty large and diverse. The lodging and feel of the hotel in general (as other reviewers have said) does feel a little dated. Would almost be nicer if it embraced the area its located in more in its aesthetic than the very basic big hotel chain feel it currently has. Nice pool and facilities. Wifi is not free, but was available in your room and reliable. Staff was helpful and you can book your tours directly with a tour agent at a desk located in the hotel.
Be careful though if you fly out of the Brazilian side of the falls as there may be a time difference. We flew on Brazil's daylight savings day and were unaware and nearly missed our flight to Rio.
Also, the hotel is expensive and offers a terrible exchange rate for US dollars. I don't recall seeing this in any paperwork I had regarding the hotel and would have changed over to pesos at the airport had we known this. We received a better exchange rate in town than anywhere else in Argentina and then the hotel screws you with what they offer. Lesson learned.