I've had the good fortune of visiting Camp Leakey with primatologist Leif Cocks of the orangutan project (http://orangutan.org.au) and they are every bit as intelligent and mischievous as described.

An important side note to this article is that (despite this observed fishing behavior) Orangutans swim, in his words, "like bricks". This leads to a lot of sub speciation either side of river systems and sadly makes migration difficult in what scraps are left of their habitat.