We completed a 4-day (3-night) tour in Sundarbans in early January and it was really excellent. Everything from the early communication with Hasan (the owner), payment, and organization was great and without any problems.
Our guide Opu was amazing, very helpful, knowledgeable, and overall a fun guy to be around. He was with us throughout the whole trip and we really enjoyed his company. The boat had a great crew who took care of everything so that we could really enjoy our trip. The food was excellent, and special thanks to the cook who prepared vegan meals for us throughout this trip (we communicated the fact that we are vegan to Hasan before we took this trip, and it was arranged without any problems).
We had our full privacy on the boat as guest quarters and our bathroom was fully separated from the rest of the crew.
On this trip, we spend one night in a hotel in Khulna and two nights on the boat in Sundarbans. We first visited some sights around Bagerhat and then proceeded on our trip on the boat through Sundarbans all the way down to the Bay of Bengal.
It is really once in a lifetime experience and I cannot recommend it enough.