The BeOS philosophy is to have a low learning curve. See http://video.google.de/videoplay?docid=1659841654840942756 (4:30 minutes). In the time BeOS was around, spatial browsing was the standard in the dominant operating systems. But today's standard is navigator mode. If you want Haiku to follow BeOS's philosophy and be an OS for the common user, Haiku should have navigator mode as default.