Xpedition is billed as a "luxury" cruise in the Galapagos. The reality is that the Galapagos islands are a long way from anywhere (600 miles off the coast of Ecuador), in a challenging environment, so any cruise line operating there will face challenges. I believe it would be practically impossible to create a true luxury experience in the Galapagos. The Xpedition is as good as you're going to get, but you have to realize that some elements will not be luxurious.
The air-conditioning on the ship strains to keep up with the heat and humidity, particularly on the upper decks (5 and 6). We passed some uncomfortably hot nights in our XS suite on the 6th (top) deck. The motion of the ship is significant. Frequently the drawers, closet door and shower door in our suite would start banging open and closed in the middle of the night because of wave motion. One night the motion was so bad that a wine glass on the counter in a high-sided, boxlike tray provided by the ship, flew out of the tray and smashed all over the place. We are not affected by seasickness, so this was only mildly annoying to us. If you are susceptible, get a patch or pills, because the ship does move a lot.
The food is adequate. Don't expect the quality and presentation you may have experienced on larger cruise ships. They are working with local suppliers, so the quality of the products they get is variable. The fish was always pretty good, as were the pasta dishes. Salads were so-so. A lot of things that should have been cold (sushi, salads, etc.) were lukewarm. I kept expecting to get food poisoning because of that, but we were fine, so I guess their sanitation is good. Like Ecuadorean food in general, we found the food on the Xpedition pretty bland but also relatively healthy (few heavy sauces, lots of grilled stuff). Desserts were very good and breads quite good.
The excursions are fantastic. The scenery is great, the animals are of course amazing, and the naturalists are top-notch. Some naturalists are better than others in various ways: some are more enthusiastic, some have better English skills, some are more safety-oriented than others. They are uniformly well-informed about the animals and plants, though. I think it's nice that the naturalists are assigned to the Zodiacs randomly, as they all have different things to offer, and this allows you to experience different approaches. (Apparently in at least one competing program, people are assigned to the same naturalist for the entire trip!)
The ship's staff are all eager to please, which is especially impressive because there's no tipping. The ship's facilities are limited, as you'd expect on such a small craft: the "fitness center" is a bit of a joke, etc. But everything is well-thought-out for the specific purpose of the cruise, which is the excursions to the islands. They have efficient systems for handling the snorkel equipment, loading the Zodiacs, etc. I was very impressed with that.
If you're considering this trip, please do a realistic self-evaluation of your fitness and health status. This is not a trip to Disneyland! There are real dangers, and we saw people who were way out of their depth and hurt themselves or others. Several had to be rescued. This itinerary is best done while you're still pretty agile and able to do a reasonable amount of physical activity. If you're unsteady on your feet or have brittle bones, this is not for you: you are going to have to get in and out of a rocking Zodiac. If you want to do some of the best excursions, you'll need to hop over the side of the Zodiac onto shifting sand in shallow waves. You'll have to pick your way over sharp lava rocks. If you can't walk a mile over uneven ground, do yourself a favor and don't go on this cruise! If you can't handle heat and humidity, forget it.
That said, you just need to be reasonably fit and have decent balance. You don't have to be an Iron Man competitor. My husband and I are both overweight and I have bad knees, but we can and do walk/hike 3-10 miles a day on a regular basis. We are both good swimmers and know how to snorkel. We managed the excursions just fine, though I skipped one that involved hundreds of stairs.
Sadly, too many people on our cruise didn't seem to have realistic ideas about their own abilities, probably because they never do any physical activity outdoors. Before you go, find out: can I walk up 300 stairs? How about 10 uneven, slippery stone stairs? Can I hop from one little boulder to another? Do I know how to snorkel? Can I swim in a current? etc. That will help you assess whether this trip is for you.
The majority (I'd say 8 out of 10) of the "long" or "hard" version of the excursions are not that taxing, as long as you're even moderately fit and healthy. I did a couple of the "easy" or "short" excursions and thought they were a waste of time -- riding around in a Zodiac was hot and usually boring. The hikes are where you see all the best stuff. If you can't manage most of the longer/harder excursions, I feel you'd be wasting your money.
In terms of seeing wildlife, there are only 6 excursions I would consider "must-do's" -- and it wasn't always clear from the descriptions which fell into that category. We were on the B itinerary and I felt the best excursions by far were Puerto Egas, Rabida, Elizabeth Bay (the only worthwhile all-Zodiac/no-hike excursion), Las Bachas, North Seymour (DO NOT MISS - nesting site for frigates and boobies) and Santa Cruz Highlands (only opportunity to see giant tortoises in the wild).
I don't mean to be discouraging about taking this cruise. Visiting the Galapagos is a once-in-a-lifetime experience and we felt it was well worth the trip. But it can be challenging in some respects, so be prepared.