Others have already given detailed descriptions of cruising the Sap and Mekong Rivers on the Amalotus; what I want to do here is provide my amateur assessment.
First, some background. We did the full package: two nights in Hanoi at the Sofitel Legend; one night on a junk in Ha Long Bay; three nights at the Sofitel in Siem Reap; seven nights on the Tonle level of the Amalotus; and two nights at the Sofitel Saigon Plaza in Ho Chi Minh City.
What works well:
The hotels were all gorgeous and luxurious, and the accommodations on the junk and the Amalotus were first class and beautiful. Both ships had rich, dark wood paneling and the facilities were excellent. We couldn't be happier with the rooms we had.
The excursions were well-thought out and well organized. We really got a feel both for rural life in Cambodia and Vietnam, and for the urban life in cities such as Hanoi, Saigon, and Phnom Penh.
The guides and tour director were all very helpful and informative. They spoke clearly enough that my father, who has trouble with accents, was still able to understand them.
What doesn't work so well:
Tipping. We were advised to bring plenty of small bills. We thought we brought enough, but we were wrong. Most of the American guests were unprepared for the number of small tips ($1s and $2s) they needed to make (I emphasize American, since the Australians traveling with APT had their tips included in their price). We were tipping so many people, so many times a day, that by the time we reached Siem Reap, we broke $60 in twenties into singles. It still wasn't enough.
So what should you do? I would strongly recommend that anyone doing this cruise bring $100 in singles and $150 in fives. The tip for the ship's crew (recommended: $10 a day for 8 days) can be put on your bill, but I think they would prefer cash, so plan ahead.
Food on the ship. Do not expect the same quality and variety of food that you would find on a European river cruise. At least part of the problem may be the availability of high-quality, hygienic food. If the choice is between variety of offerings and the health of the passengers, the cruise line has understandably chosen to emphasize the latter. I also suspect, but don't know for sure, that they may also have a legal obligation to use locally produced food rather than imported (e.g., Cambodian-produced ice cream rather than imported).
I found the best food on the ship to be the fresh fruit and the fish. The meat tended to be tough. The worst, in my opinion, were the desserts (with the exception of the fruit).
Another problem was the cruise line's policy of dividing the passengers into defined and permanent groups. This policy seems to be driven by the issue of tipping: 1) since guides may serve for a number of days and only be tipped at the end, it was important that each guide receive the proper amount of tips to reflect the work; and 2) since the Australians already had tips included in their price, they needed to stay with their already-tipped guides.
So why was this a problem? Well, in our group alone, there were at least three people with mobility issues. Since the cruise line couldn't offer a "slow-walkers group," their only options were to either choose not to go on an excursion or to try to keep up at the best of their ability, which was sometimes difficult.
Some people made friends with people in other groups, but they were not permitted to do excursions together, since any movement of people from one group to another would throw off the balance of tips.
Finally, and I'll have to put this delicately, there were some strong personalities on our cruise. By being kept together for the length of the trip, one might be trapped for 15 days with someone who one didn't merely dislike but was unable to stand.
What I would recommend to AMAWaterways is that they can solve many of these problems by making most tips inclusive in the price. This would diminish the need to bring a small suitcase of ones and fives and permit them to tailor excursions by ability.
Please do not take these criticisms and suggestions as unhappiness with our cruise experience; my father and I greatly enjoyed our cruise experience and do not regret our decision to go. I would only suggest that future passengers adjust their expectations to the reality of the experience on the ground. Cambodia is still a relatively new tourist destination and one shouldn't go expecting the Danube.
One last issue: this really isn't a solvable problem, but some guests were annoyed that due to lower water in the Tonle Sap lake, our transfer to the boat involved a 5.5 hour bus ride. This is what happens when one sails in the dry season, but it came as a surprise to some guests.