My husband and I did this cruise as part of our honeymoon and it was excellent. We were very glad we opted for the 2 nights as the 2nd day's activities were less crowded (only 4 of us). The staff on the main boat (headed by David) and the day boat (headed by Son) were so attentive friendly and honestly couldn't do enough for us. Halong Bay itself is very crowded with lots of boats etc therefore you can see rubbish in the water etc. The food provided was lovely and the activities were very enjoyable.
I would highly recommend this trip.
To make it a more enjoyable trip for guests I would suggest updating the soft furnishings in the sofa area (they are a bit tired and worn looking- a few towels could have been replaced also), wifi would be good on at least the main deck (we know another boat had this as we spent the 2nd day with a couple whoseboat had wifi).