alternative implementation of the core functionality
Since it isn't working anymore after recent google changes and the author of this script seems to have abandoned it I have been working on an alternative that implements the most important features: the mark-read and the rollover-popup. Additionally it does auto detection of the optimal refresh interval, it has no config options, it will figure out everything on its own.
This is the first release: http://userscripts.org/scripts/show/104040
Its not a fork, its a complete rewrite from scratch based on a slightly different concept.