Tab Groups work like this add-on except the manager was a bird's eye view rather than outline. You could see thumbnails of your pages in the group and drag and drop thumbnails between groups. Opening a group would open all tabs in the group. Works really well.
https://support.mozilla.org/en-US/kb/tab-groups-organize-tabs

I will disable my The Great Suspender add-on and see what kind of effect it has on the tabs. It looks like the green X does kind of the equivalent. The difference might be that The Great Suspender suspends tabs automatically after a certain amount of time.

I think the following statement by the author gives him some cred; he's not just anti-MS or anti-UI changes. His opinion is based on experience.

"Having used Windows 8 on desktops, a laptop, and on a tablet for almost a year now, I'm considerably more skeptical."

By using, I assume he means his daily driver.

This is a great little app. I found my pop-up sound. Enjoy.
http://www.freesoundfiles.tintagel.net/Audio/free-wave-files-animals/frog_1.wav

There is this one, but it's a little much.
http://www.freesoundfiles.tintagel.net/Audio/free-wave-files-animals/frog_2.wav