This has been on our bucket list for some time. It was very enjoyable with a good mix of relaxation and activity. Some of the APT specials are not to be missed - the Grand Imperatore train (albeit some of the air con failed on a very hot day) and the Vienna Concert in the Lichtenstein Palace.
Food was always excellent with many choices and the staff very willing to keep you pleased with a smile.
Entertainment was limited to the space available, but overall enjoyable.
Our room was in the lowest level and well maintained, comfortable and with no noise issues. Given it was nearly the cheapest cabin there was nothing to complain about. There was sometimes a smell, which we worked out was only while in major ports, so probably unavoidable. Wasn't an issue on any night we slept on the boat.
Cruise operator could make it plain that low bridges will mean top deck is unavailable for 5-6 days while on the Rhine/Danube canal. I know this is mentioned but perhaps made a little clearer.
The dining experiences at the special tables in the stern were a highlight, for both food and service.
Apart from these small issues (to us at least) you could not fault the whole experience.
This is our third APT/TravelMarvel trip and we plan another.
Cabin was the nearly the cheapest so it was our choice to be on the low level. Service, comfort and amenities excellent. Happy to use this level of room again.