WE recently returned from our Atlas Cruise and absolutely loved it
A few things I wish I knew beforehand
The Argentinian peso is not stable and there is an "official" exchange rate and a "blue" exchange rate. Check with your credit card to see what they use. Most of the stores will take US dollars and most of the ones near the port in Ushiuia posted their exchange rates (which ranged from 200 to 340 pesos per dollar, "official" rate was 187)
you can take liquids through security for domestic flights in Argentina , and there are no drinking fountains at the airport. Fill up your water bottle before you leave the ship.
you can take a personal bag and a carryon on the charter flight, they didn't weigh our backpacks, but did weigh all the roller bags. One couple with camera equipment was told their roller bag was too heavy, so they took out a zoom lens and put it in their backpack and were able to take everything on the plane.
Cruise itself was wonderful. you need to be flexible as weather conditions can change. We were in the last group on the first day and some brush ice moved into the landing site, so we got a zodiak tour instead, but there were several landings that we were able to do, so all is well.