Still going strong - Extremely useful Rated 5 out of 5 stars
I don't know about the fellow's situation who mentioned all the problems... seems like something else must be going on in that situation, even if disabling this tool seemed to stop them. Sometimes the source of a problem isn't so obvious, even if it seems to be so..
I have no affiliation with the developer...
I have been using this addon for years now ...with absolutely no issues -ever, And the memory usage has been improved over time, as well. I consider myself to be a heavy user (engineer/developer/researcher) and I use this 'to death'.
It never fails, I have never lost any links, it is a key tool for keeping my projects well organized and distinctively manageable (one from another).
I typically (on average) will have about 15 windows open with from 100 to well over 150 tabs in my main browser. I am usually running two to three browsers (different types and versions, and for various reasons), and the other FF ones typically run about 10 windows with about 50 to 80 tabs. Typically 1-3 windows will be a 'collective' for a project or job. Session Manager makes handling this scope and managing this type of usage a breeze. Bookmarks simply cannot support this need - I use bookmarks for maintaining library-collections of data (references)....
...So if I was at an actual library, bookmarks would be like the catalog to the stuff on the shelves, and Session Manager would be collections of open books ++plus other stuff (that never makes it to the book shelves) on various tables, or in conference rooms... the dynamic aspect.
Plus, Session Manager provides a great tool for going back in time and observing the "state of operations" for any given project on any given day - or during any period. Bookmarks, even with tagging simply don't provide the tools for real dynamic projecting and research management.
The developer is diligent in keeping up this tool, and helping people, and listening to feedback for development.
I see session management as an integral key component to using browsers and the web in any practical manner. The tool provided here is a necessary one for anyone who seriously relies on the web for research, communication, and working.