Although we had high expectations based on comments and praise from family and friends who had visited before, we were startled and amazed at how magnificent is this natural landmark. Although there can be a good bit of waiting on line - not too bad, really - and then walking to get to the really good spots, it's well worth it.
We were additionally lucky to see a young five foot caiman sunning about 25 feet away and a catfish swimming right below the catwalk that had to be about four feet in length, with its buddy of more than three feet. Also several tortoises were sunning out on the rocks, not very close but they do show up clearly in photos - the largest had to be nearly 36 inches long.
Planning note: Because we exited not where we entered, we missed getting photos of some extraordinary large photos (on display outside the souvenir shop) of when the falls were dry, in the '90s (?), and also purchasing a classic Iguazu t-shirt.