Absolutely phenomenal multi-day trip. All the other reviews talk about what you can see on this trip so I will focus on what to expect on the boat.
First of all the crew, because they ensured our trip was a 10/10 experience. Our guide was Jeffrey, his father was a ranger in the park and he grew up here. We are avid birders and he was able to identify every bird off the top of his head by sight or by song. Our captain and first mate were great at spotting animals in the trees or in the water, and positioned the boat so we could view them. One night we heard a fish owl and our captain scrambled along several docked boats to get the shot for us! Our cooks name was Yummy and she prepared us 3 delicious meals per day as well as several snacks. The plantain pancakes were AMAZING!
The crew were also very accommodating. The trip centres around the 3 feeding stations but we preferred to see animals in their natural environment. We mentioned this and it was not a problem, just let your guide know when you're done with the feeding station.
The boat is a klotok, all boats on the river seemed roughly the same regardless of the company, I don't think shopping around with different companies will get you a better or worse boat. You get the top deck to yourself, which includes a bed (with mosquito net), a table with chairs for meals, and several lounging chairs for viewing the nature around you. Downstairs is the kitchen, crew bunks, and a toilet shared by both you and the crew. The toilet is a Western toilet, not squatty potty, but you cannot flush toilet paper and will have to learn how to use a bidet or hand shower to clean yourself afterwards! However this is the norm in all of Indonesia.
There are lights and a charging point to charge cameras and phones on your private top deck. We brought headlamps and portable backup phone batteries but they weren't necessary.
Special note: try not to leave electronics out overnight as there is a lot of moisture. Bring a ziplock bag and store in your bag/suitcase overnight. However, my Samsung S8 is waterproof and it was fine to lay beside me overnight.
The first night we docked alongside some mangroves, where fireflies prefer to live, and fell asleep watching the fireflies. The second night we docked at a research station in order to walk through the trails on a night walk to look for nocturnal life. I have arachnophobia so I just stayed on the boat, my boyfriend went with Jeffrey for about an hour and saw loads of creepy crawlies! If you aren't too interested in the night walk I would recommend asking to just have the boat parked away from other boats instead as the first morning, where we woke up to gibbons hooting and the morning chorus of the birds, was absolutely magical.
The one issue we had was the crews all joined together to play games directly beside the boats until 11pm and we finally asked them to quiet down as we found we would wake up at around 5am each day and wanted some sleep!