We just returned from South America on board of Mercury. I don´t recommend it, unless the price is very good.
We were on the same ship on july to Alaska and it was completely different. They changed the cruise director and the whole staff of entertainment, both not good at all, specially the cruise director. There were very few activities on board. The youth program only worked for kids until 6/7 ys. For the older ones, the program did not meet their needs and they were running all over the ship, including my son.
The ship was too crowded and you could never find a seat on the buffet for breakfast or lunch.
The night shows weren´t good as well.
The wake up call system was not working and we had to ask house keeping to call us in the morning, which did not work sometimes. Ordering breakfast in the cabin did not work. I order once and I´m still waiting.
The shore excursions were very expensive and not much to see. For instance, you had to be on a 5 hs trip (2 ways) to see a bunch of penguins. I prefer the Penguin Encounter in WDW. The difference is that they are in their natural habitat. Americans and Europeans seem to enjoy this more than Brazilians like me.
As my husband says, we paid an excellent price, but you have to suffer!