Ekspos Image Viewer is platform independent Java image viewer program. It support most popular image format: JPEG, PNG, and GIF, where additional image format can be added through Java ImageIO plugin. It consists of 2 parts: shell browser and viewer. Shell browser allows you to navigate your image collection and you'll be able to browse images in tree, detail, list, icon and thumbnail view. The viewer provides progressive view of images with zoom and pan capability.
The only viewer for OS X with the simple design of a file name pane (w/o the clutter/slowness of thumbnails) and an image pane. Click file name, image shows. Inept viewers use thumbnails, or have limited file navigation, or need a double click, etc.
Base bones. Probably still under development. Fit to screen feature doesn't seem to be working perfectly.
Even in its present state, this viewer wipes the floor with unimaginative garbage like Xee.