User blog comment:Ieatrice/New Image Galleries Available in Labs/@comment-184543-20141024150844/@comment-452-20141102225646

When enabled, all thumbnail and slideshow galleries use the new format, unless the gallery has "navigation=true" set, which is automatically set if any images in the gallery have "|link="

Edit: I haven't checked whether or not a page needs to be purged after enabling it, but I assume that since the new gallery is javascript-based, that it will not require purging each page.