We've just come back from a Liberty Cruise. Went on this excursion - we didn't walk up the falls but went down to the beach instead - not the nicest beach I have ever visited I have to say - only famous for that James Bond scene with Racquel Welch!!!
The guys who did the falls said is was hard work and be prepared to get soaked - I saw some people doing it in bare feet which didn't seem a good idea!! It takes a good hour - not because it is a long walk - just a slow line with everyone holding hands
As an aside I reckon this is not the most environment friendly activity - all those people doing this day in day out must eventually cause some damage