Can work on almost any webcomic/manga page, preloads 5 or more pages ahead (or behind), navigates via ajax for instant-page-change, lets you use the keyboard, remembers your progress, and it's relatively easy to add new sites
You can re-enable the script using the Greasemonkey menu (Userscript commands / Webcomic Reader - Enable for this site)
How do I re-enable for a site? [workaround found]
I disabled the plugin for a site that's changed, in order to figure out a new means of getting the prev/next/img/etc elements the script needs. But there doesn't appear to be a straightforward way to re-enable it for the site.
A workaround:
I did ultimately re-enable the site by exporting the settings JSON, removing the site's settings entirely, and then re-importing. Simply removing the 'confpag':'dis' node would also work.
But that doesn't seem like an easy thing for most users to do.