We met a German backpacker in Puerto Iguazu who was on his way from Argentina to Brazil, and despite being right there, he wasn't sure if he could be bothered to see the waterfalls because he had seen plenty of waterfalls before. We were not quite sure what to expect either, but we have never seen anything quite like this! The scale is overwhelming. The thunderous crash of thousands of litres of water falling over the edge in front of your eyes is truly awesome.
The Argentinean side of the falls gives you access to several walking trails with different view points, and allows you to get up close and personal with the water, including going under the falls in a speed boat!
Overall the whole experience was amazing! Iguazu Falls is one of the new seven wonders of the world for a reason!