I have been using Xmarks for a very long time (since it used to be called Foxmarks).
Actually, I had stopped to use it some time ago because of an annoying issue and had switched to Firefox Sync.
But since I need to use again several types of browsers, I am giving Xmarks a try again, .. but face the same issue again.
So what is the issue ? Simple : when I ask Xmarks to synchronize (in Firefox, using Tools > Xmarks > Synchronize now), it starts but never ends : the Xmarks window opens, I can see the animated gliding bar, it shows "Bookmarks : ready" (the other features are deactivated) and it stays in this state endlessly. I already tried leaving it to sync a whole night, with no result. In the end, I simply cancel by closing the window. But I can see between my various computers that they don't get synchronized.
To be fair, I have many bookmarks, probably over a thousand. So I would understand if sync was slow .. but not stuck !
Environment : Firefox up-to-date, additionally Chromium browser. OS : Ubuntu or Windows 7.
I am ready to send by PM an export of my bookmarks if it helps.