The preview seems to be not working, see http://test.bytesforall.com/ for a preview that is more full-featured anyway, until I have a fixed version up.
Note: The fact that the preview doesn’t display on wordpress.org does not necessarily mean the theme is broken, not at all.
Here is a quick overview over the features: http://wordpress.bytesforall.com/wordpress-themes/montezuma/
The auto slideshow for default WP galleries is here: http://test.bytesforall.com/2008/06/post-format-test-gallery/
Being a brand new theme there might and probably will be issues. The theme is tested though.
Note: This is not the old Montezuma from 2007, I am just using the name.