I'm considering to book a 3d/2n safari at Kinabatangan river with Uncle Tan but everybody tell me that, despite they offer a fantastic trip, the accommodation is very, very basic. I've also heard about other kind of accommodations like Bilit Adventure Lodge (more comfortable but affordable for backpackers budget), somone has stayed at Bilit Adv Lodge?
Our first aim is seeing jungle's life, so any comments?
Thanks!

You should inquire as to how many boat safaris and how many treks the price includes at Bilit. You may be paying the majority of your money for accommodation and not wildlife viewing. Uncle Tan's 3D/2N package includes 5 boat safaris, one day trek, and one night trek. It also includes lunch at the base office on the day you go to camp and the day you return. Yes, the accommodation is basic, but it's only two nights. Most can tough it out for such a short time in exchange for what they see.

We are just back from Uncle Tan. The facilities are very very basic but the overall experience is great. The safaris are good value for money, the food is very good and the staff really go out of their way to involve everyone and create a fun atmosphere. All in all if you can rough it out for 2 nights, it is great fun.

I don't know how much Bilit Adventure Lodge charges...but they may allow you to pay more for additional boat / walk trips. I do know that the two boat trips Uncle Tans has (the trip in and out by boat) are not available at Bilit since you travel there by car.
But the accomodations seem to be a bit cleaner and if you are insistent on amenities like a private bathroom in a private room, rather than a communal shower/toilet set-up, then don't go to Uncle Tan's.
As both #1 and #2 point out, Uncle Tans will keep you quite busy with the possbility of spotting wildlife...at all hours and in different conditions. On a boat trip you will see different things than on a walk/trek....even at the same time. Outside of mealtimes, there really is only one "down time" at the UT camp...between 1 and 4 PM when it gets pretty hot. Some people use that time to take siestas in their hammocks, play volleyball/soccer, to sit around and chat, or even to do a solo walk on the trails around camp. One can see birdlife at that time, although most mammals are hidden up sleeping. Still, I've seen orangutans feeding and some other interesting creatures at that time there.