All fixed, works fine with sync Rated 5 out of 5 stars
The developer fixed the problem mentioned in my review for version 3.4, and 3.4.1 now works fine with sync.This review is for a previous version of the add-on (188.8.131.52-signed).
No longer works with sync Rated 4 out of 5 stars
Version 3.4 no longer works with FF sync. If you mark a page of links (like in a bulletin board) as visited using the "mark all links visited" feature, they do not show up as visited on another computer after a sync. It happened right around when I finally updated to FF8, and persisted with FF9, and not realizing that Link Visitor had updated, I thought it was a problem with FF and not Link Visitor.
However, I then noticed that Link Visitor had updated from 3.3 to 3.4, so I reverted to version 3.3 just to be sure, and it was working just fine again.
So, something in the changes to 3.4 caused the visited history records to not propigate via FF sync. They stay marked as visited on the original computer, it just never makes it across to the synced computer.
For now, I'll stick with 3.3. If this gets fixed, I'd give it a full 5 stars.