We really enjoyed the cruise. I fell in love with penguins at the two penguin sanctuaries we visited; you can get up really close to them at Puerto Madryn. Just be aware that around the Horn can be really bumpy. We were on the Mercury, and at times the waves were so high that water came through window seals on the higher decks into the centrum lounges and casino. Just depends upon the cruise and what storms are out there, I suppose. We departed Buenos Aires mid January.
I've heard that the western coast of South America is not so bumpy going southward. I don't know for sure, but it was pretty rocky going northward toward Valparaiso. Same as Mexican Riviera; going southward is smooth as cream; returning north, it's bumpy.
However, the sites made it worthwhile. If you'll send me an e-mail to craven3 @ adelphia. net (omitting the spaces, of course) I'd be happy to send you my port-by-port reports that I sent to friends. Some of the ports are great.
If I were going to do it again, though, I'd go on Marco Polo (Orient Line), Quark, or Holland America because those are the only three that actually offer something in Antarctica. Celeb only offers a $2500 flyover, with no refunds for foul weather. These three let you get in Zodiacs and wade onto the ice. See the giant penguins for yourself. That kind of thing.
I don't remember a pre-excursion to the falls, but it's super easy to arrange your own air and hotels and then get up to the Falls on your own for a stay.
Charlotte