There was some discussion on thunar-dev whether or not a Columns View should be included in Thunar. This feature originally appeared with NextSTEP and was imported into Aqua Finder by Apple. In the UNIX/Linux desktop community only a few people know about that feature.
The idea behind the Columns View is to allow the user to easily browse the directory tree in a consistent and fast way. Personally I still think its a power user feature only, because I have trouble to imagine that newbies can get used to it.
The screenshot below shows the Columns View in Aqua Finder:
I hacked up a simple implementation of a Columns View for Thunar. It looks like this (note that it does not include most of the usability of the implementation in Aqua’s Finder):
The tarball with the implementation is available here. I expect this feature to be removed from CVS in the future, so there’s the link in case you are interested.