X-Marks Lives :-D Rated 5 out of 5 stars
The best - end of discussion.
The news that X-Marks was shutting down in January was met first with disappointment, followed closely by bewilderment regarding what to do in its absence. It is remarkably reliable, widely compatible, and integrated to such a degree that one can very easily forget it's there altogether. Once it's configured on a browser, aside from the rare network issue or password / PIN change, one probably won't have to give it another thought. It becomes extremely easy to take for granted - which is why the news was so startling.
I use X-Marks across multiple computers, operating systems, on IE, on Chrome, and on multiple versions of Firefox, and seldom have the slightest issue. It just does its thing and gives me one less thing to worry about. I run plenty of extensions on FF, but there are only a few I truly could not do without anymore - X-Marks is one of them.