Thunar 1.0.0 running in Ubuntu 9.04
I think Thunar interface couldn't be more simple than it already is, and it will also satisfy users who like intuitive and easy-to-use applications. Except for the menus, it has no toolbar, but only a sidebar with the common places, like Home, Trash, Desktop, Filesystem or Floppy drive. The rest of Thunar's main window is occupied by the files and directories widget itself. The side panel can be configured to show direct shortcuts, or display a tree view of directories.
Thunar allows you to set emblems to files or folders, it permits modifying permissions with a simple and clear method, and it will allow to choose default applications for opening different types of files.
By default, the location bar is available in Thunar as a separate window using Ctrl+L. This way the new open location window steals focus and prevents access to the main window. Instead, you can choose to change this behaviour with the View -> Location Selector menu entry, from the Pathbar Style to the Toolbar Style. I think the default behaviour may be less confusing to new users, but the second approach is better in my opinion. Also, a very good thing to have them both and the option to toggle between them.
Image previews, file properties and the toolbar style location bar
A powerful feature of Thunar is the ability to create custom actions, for example for extracting compressed files, comparing files etc.
Files and folders can be sorted by name, size, type, modification date, ascending or descending, and the size of the icons can be increased or decreased. They can also be shown as icons, as a detailed or compact list. Besides these, Thunar also allows image previews. There is also the option to set the current file as wallpaper, if it is an image, but it didn't seem to work for me.
Tree view and preferences
The Preferences window allows to configure single or double-clicking to open files/directories, icons sizes, emblems behaviour and the displaying of thumbnails.
Documentation is available as a HTML file on the local disk (if installed properly) and it is accessible via the F1 keyboard shortcut (or the Help -> Contents menu entry).
I noticed Thunar will not offer the possibility to mount volumes (like separate partitions) like Nautilus or Dolphin do, so you will have to do this manually from command line.
What can I say? Thunar is a lightweight application, but under the hood there are many features and an impressive approach. It's true, most of them are typical for any file manager and are a must-have even for a lighter application of this kind, but Thunar succeeds in implementing everything in a nice, compact and intuitive interface. A very good alternative to Nautilus and probably the perfect file manager for Xfce users.