First off, this hotel sits on a stunning property. Your access to the waterfalls cannot be compared. You can take a 7:30am trail walk to see the falls without the tourists!
The breakfast buffet alone is worth the five star review...Egg omelet bar, egg benedict and other hot options, fruit, waffles, meats and cheeses, pastries, all the breakfast greats.
But I want to speak of the service. The staff go above and beyond! I had left my camera in the back of the taxi from the Argentine side of the falls. The front desk not only tracked down the cab driver and negotiated it's release (Not kidding, the cab driver demanded money to bring it to the hotel) but also arranged for financing since I had no Brazilian dollars! They rescued a cherished item for me.
I *cannot* express how amazing this hotel is. I don't stay in high-end hotels often (I tend to go for quantity of trips over quality--mostly mid-range hotels) but I will go back to this hotel and stay for a week, easily.