Traveled last August with my girlfriend and had this amazing experience (sorry for not leaving comment any sooner).
Before you arrive: Arif and Dessy were kind and very trustworthy from the very beginning. They took care of everything and offered their help on any issue they were able to help with. Booking flights, any additional info.. whatever they could help with, Dessy is in charge for you.
About the trip itself: We spent 2 nights on the river. To be fair I must say it was the exact amount of time you need. If you go less you do not get to do the full experience. More time is repetitive, since there is only 3 orangutan parks open to visitors (couple of friends did that one).
We accesed the parks as everyone else does, same time for every boat. We notice that Arif did not mind at all to go the last one, to stay as much or as little as we wanted. We actually stayed on 2/3 parks a while after everyone left. There, alone with the orangutans couple meters ahead. AMAZING
On our second night we did a night treckking. We saw nobody else doing this. REAL COOL STUFF. We saw a lot of animals with the local ranger and Arif as guides. You like nature? ask Arif for this, you wont regret it.
About the crew: Arif speaks good English. He has a nice conversation and knows when you need your own space or when you are looking for some conversation or fun facts. The other people around the boat are always the same guys we were told. You wont notice they are there unless they spot something its worth a watch (crocodiles, cool birds, wired reptiles...). Very good local cooking is done by the cooker too.
About the price: I can just say we saw people paying much less and they were disappointed on how their trip was run. Good food, good crew, good guide. Fluent English speaking is not as common as you might think over there. We did not share the boat, altough I must say there is room for another 1/2 people, with you not even noticing.
My very personal opinion: Arif is the kind of guide you want to have. He has "the twinkle in the eye" you can just see on people that love what they do. That is the most important thing for me, he makes your stay really enjoyable and you do learn a lot by his side.
Animals we saw: Orangutans, Makakos, Narigudos, Crocodile (two types), big reptile (like the komodo, smaller version). BIG ants. Night trekking: Frog, Bat, baby tarantulas, Buterfly...cool birds... and lot more of other I surely not remember now.
Thank you guys, see you on our next adventure!
Oscar Lima & Laura Quiñones