Near-broken for me Rated 1 out of 5 stars
After a lot of issues and errors with installation, I finally got things working. Unfortunately, running Firefox 14, I found the add-on appears to be broken. Even though it claimed to sync properly, it did not actually download anything and bookmark changes in other browsers were not reflected. I can't say it's broken outright, as some users may have success, but I certainly didn't.
Shame, because LastPass is an excellent add-on and pretty well maintained. I'd like to see Xmarks reach the same level of quality and reliability as a service.