Have been using the module for a few months and finally decided to figure out how to enable the lightbox effect and am documenting it here to help other new users.
At the Manage Fields -> CCK field -> Gallery Formatter, enable "Link slids to the full image" and for preset image "None (original image)"
Configuring Lightbox2 is a separate issue. Go to Site Configuration -> Lightbox2 -> Page specific lightbox2 settings. For myself I chose "Load on every page..." Works great.
Lightbox2 and Shadowbox seem to be great ways to allow people to view full sized images. It is so easy once it is figured out!
