This would be my ultimate vacation. Have only gotten as close as Thailand.
http://www.intrepidtravel.com/us/borneo
http://www.imaginative-traveller.com...t-asia/borneo/
We have taken two trips with Imaginative out of the UK. Different experience from American type tours. We went to India and Egypt. What I like is the amount of info and levels of amenities on the different trips.
I have found that the Commonweath country citizens travel far wider than Americans and therefore have some pretty interesting tour groups.
I also found Gecko Tours out of Australia.