My wife and I took a two day (1 night) Mekong Delta tour, privately organised with Tiger Tours. Communication beforehand was good and we were impressed with their eagerness to tailor-make the tour for our needs.
We chose to do a private tour because we wanted to experience a the Mekong for more than a day and wanted to see a lot in a short space of time - our experience in Vietnam was always that the most efficient way to do this is with a guide who can coordinate well with local partners. The whole trip was well implemented and highly professional. We saw lot -including local river tours on boats and sampans and amazing musical performance, cycle rides, a local homestay, a floating market, loads of food and the experience of numerous small businesses/craftworks etc that make up the heart of Mekong culture. There's probably more that I've forgotten to list!
Our guide (Joy) was great fun to be with. Very warm, very informative but also with a really good instinct for letting us to do our own thing and experience things for ourselves wanted to. On day one she told us that apart from her job in welcoming use, her mission was to make sure we got more food than we could (she well and truly succeeded!).
We were really interested in understanding the culture and history of the region and vietnam as a whole and she was very engaged and willing to share things. She even had slide shows on her tablet about different aspects of Vietnam.
What struck me most about her is that she immediately just seemed to "get" what we wanted out of our visit and arranged it accordingly. For us this was quite focussed on culture and history but I got the impression that if you had other interests, they would probably be seen to with the same attentiveness.
Finally we received all whole stash of photos from the trip taken by our guide and a friendly email to get in touch for further advice. Would use their services again and recommend strongly!