I lived in Galapagos for four years (1999-2002) and had the chance to get to know this archipelago quite well. Made up of over 100 islands straddling the equatorial line, 600 miles offshore from Ecuador, a dozen are fairly large, and each offers a distinct combination of landscapes and wildlife. Sea life is commonly underated by Galapagos visitors. Where else can you swim, at the same time, with penguins and tropical fish? Swimming is part of the adventure. When asked about the highlight of their visit, many say "swimming with the sea lions". But if you're lucky, you can also get too see dozens of giant tortoises in the wild. In fact, Galapagos is one of those very rare places on the planet where, like in the film Jurassic Park, reptiles still dominate the landscape (now more than ever, as the National Park has finally gotten rid of the thousands of wild goats that had taken over Isabela island).
80 cruises ships ranging from 8 to 100 passengers, and run by about 35 diferent operators ply the Galapagos waters. Extreme luxury, to converted fishing boat, there's a wide range from which to choose. I prefer the smaller ships, which can give you a more intimate visit. These come in all comfort levels. But larger ships provide more space and on-board services and are sturdyer when seas are choppy.
Some are surprised to learn that about 30,000 people live in Galapagos. There are 5 settlements - the largest is Puerto Ayora on Santa Cruz island, with nearly 20,000 people in town and in the highlands. The government is trying to slow immigration, knowing that as the population grows, so do the threats to the fragile island ecosystems.
A typical visit to the Galapagos consists of a 7 night cruise, which give you the opportunity to explore the far reaches of the archipelago. If you want, you can extend that visit by staying on in a hotel and do some independent exploration. There are shorter cruises for those with time constraints (a pity - it's so far to come, you should make the best of it), and a recent development has been the island hopping visit, which have you zooming between the three main populated islands for a look at local attractions.
I did a few cruises while living in the Galapagos - on a big ship and on small ships - and always had a wonderful time. People on board were wide-eyed and enthusiastic and quickly developed a great team spirit. After all, we were in the middle of the Pacific together.