FF 12 has overlay problem so can't access all Rated 4 out of 5 stars
LOVED Gmarks with v3.x and earlier.
With Firefox 12, if you do not scroll down fast enough (or it stalls while scrolling, which happens often), you cannot get to certain folders or unlabeled marks before a folder's child list opens and covers the parent list preventing access to the parent list. And there is no way to close the child list without leaving the parent list too and starting over.
This was not a problem with v3.x. That version truncated the mark labels so that the child lists always opened to either one side or the other of the parent.
Another problem is that even when you have a child list that doesn't completely cover the parent, you still cannot scroll up and down the folder list. The current folder's child list just stays open. This was definitely not a problem in 3. You could choose up and down the parent list of folders and child lists would open appropriately.