Now includes a configuration tweaking tool. Some options are not as exposed as the more common ones, changing them is somewhat similar to using regedit. See the shortcut in Start menu.
You can now tell Viewer2 not to stretch or shrink images to fit on screen.
When viewing images, the next and previous images are preloaded for instant switch.
Browsing directories is now quite usable, directories are shown with a yellow border around a preview of the first image in that directory (or a directory icon if no images are found). Use the config tool to enable this.