Marc, we are doing our own thing going from Buenos Aires to Iguazu Falls in February. We booked round trip tickets on Aerolineas( www.aerolineas.com )for $198.60 p.p. (this includes tax). We are staying overnight at the Sheraton Hotel for $184. per night. The ship's excursion goes up and back in one LONG day (11-12 hours) so that's why we decided to stay over night and do our own thing. The ship's excursion is $795. p.p. and so far including our RT flights and hotel we're still under $600!!

I think if you can figure out where to stash your luggage, you should just fly up and back in one day. Even spending a short time there is better than not getting to see it at all.