Cascata delle Marmore is an artificial waterfall and although beautiful, is a bit contrived as the water changes from a weak/modest output to a roaring waterfall. I would highly recommend starting at the lower falls and then working your way up after you've seen the falls begin. There are very few places that you can see the water along the main trail so don't count on seeing the water as you hike up except for marked locations. During our trip, all of the easy paths to see the water were closed and the only real option was path 1, listed as an "average-high" trail but was more steps than not. Doable but expect to have sore calves if you are not used to climbing. Because "Lover's" balcony was also closed, there were no water views until we reached the high "Specola", a great location to see the upper falls and accompanying rainbow.
Our GPS was somewhat confused in getting us there. It turns out the lower falls are right off of Vocabolo Collestatte Piano. The ticket booth is as far away from the entrance as possible resulting in a rather long but flat walk to the falls. The cost Nov 2010 was 7 euro. Restrooms were 30 cents and were relatively clean but typical in Italy lacking a toilet seat. Throughout the area are picnic tables and benches so unless you are there during the peak season, sitting should not be an issue. The views from the lower falls are spectacular and there were even covered places if you come in the summer. We saw several people with water ponchos but at the locations available to us, did not have a need. I suspect that it is wetter at some of the locations closed to us.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.