Slow, buggy Rated 1 out of 5 stars
1. Too slow and unpredictable to be useful. Took at least 5 minutes and many reloads for a new bookmark to appear in the online account. I added two more that never showed up in the online account. I gave it half an hour then uninstalled the add-on.
2. Unstable installer, reported error that wasn't error. On first pass, installer failed with meaningless message "Version 1 accounts are no longer supported". I was installing version 126.96.36.199. Then it sent me to the download page for same version I had been trying to install. I installed it again exactly the same way and no error occurred. Not exactly a confidence builder.
For those reasons I do not trust the privacy claims.