Gawd, some people are quick off the mark... perhaps a little too quick this time though, the original 1.31 uploads to userscripts.org and crx.chizzum.com were withdrawn and replaced a few minutes later with the proper copies, so you might want to grab another copy now just in case you managed to pick up the withdrawn version.
For URs with comments, the UR popup in 1.31 now shows how long ago the last comment was posted - there doesn't appear to be any way to tell whether comments have been read or not read, so showing the age of the latest comment is as close to fulfilling gohamstergo's suggestion as we can get right now.
More importantly, it also fixes the bug that causes multiple URO tabs to appear if the user selected a non-English UI localisation in WME. This was originally reported a couple of weeks ago, but I couldn't replicate it then in either Firefox or Chrome, and in Firefox on my systems it still isn't obvious - although the bug is present, the script degrades gracefully without any obvious sign of failure. It's only in Chrome, and only in the past few days on my systems, that the multiple-tab effect has shown up. Not sure why other users started getting hammered by it so much sooner than me, but at least it's now sorted out...
Firefox+Greasemonkey version: http://userscripts.org/scripts/show/145186
Chrome packaged version: http://crx.chizzum.com/UROverview.crx