Lens it UP works on most HTML-based galleries where thumbnail links directly to a fullsized image.
This means:
Additionally the latest update supports Apache's "Index of" directories, but lensing them up won't provide thumbnails for the images.
Lens it UP will not work on galleries, where thumbnail links to another page or a popup window with an image, or if there's no thumbnail at all.
Additionally it will not work on password protected websites, websites that require accepting certificates, websites that allow their content to be linked only within their own domain (most of TGP gallery problems), or websites with very complicated rewrite rules.