Please read! Rated 5 out of 5 stars
It seems the developer (Ithinc) of the original Tab Utilities is not gone, deceased or what so ever. According this comment: https://addons.mozilla.org/nl/firefox/addon/tab-utilities/reviews/497922/ and at the top of the add-on description he/she wrote the add-on will be updated at the end of September. I advise Ithinc and Stux to work together to make sure there is only one solid, regularly updated add-on.This review is for a previous version of the add-on (1.6pre7.1-signed.1-signed). This user has a previous review of this add-on.
Thanks for the update jeroenvrp. I had kept an eye on that page but hadn't noticed that developer response. I will try to get in touch with ithinc.