Because the octatrack is pattern based, and bescause i'm way too used to compose in a linear way, i had difficulties wrapping my head around the arranger at first.
But actually, i see many good point to it.
During the composition part, i usually do a group of, let's say; 4 pattern, 64 bar each, looping several time, so i can developp a melody or a chord progression on it more easily.
Starting messing with the components for a polished song, i bring on the arranger the basic parts of my song (intro/verse/chorus or sort of) and start messing with mute in the arranger.
Actually, and this is perhaps the most interesting part as well as the "scariest", i feel the arranger mode composing method a bit like making old school rough drawing for product design. you throw guidance lines, as well as alterations, like mutes or scene and then your first intrications, like muting/unmuting not specificaly at the beginning of the pattern.. then... you take some distance, and let this self-induced creativity path leading you to fully composed piece.
Trial and errors can contribute to put on relief some odd aspect of the track. that's what i like with the arranger. but it is also why it is not the most user friendly way of composing, for me at least