does that mean, most opera users lost their bookmarks forever if they don't do a manual search? ...
Again, a lot depends on the old version that stored the user's original bookmarks and where it stored them. New Opera versions can import bookmarks from old versions, but the new versions currently look for the bookmarks file in a certain named place on the computer's hard drive. If the bookmarks file is stored in a different-named location, the New Opera won't "see" it, so it won't import it. In that case, the user would have to manually track down the old bookmark file location on their drive and copy/move the file to the location that New Opera needs it to be in, before it will import it.
I'm not an Opera Link user, so I can't address whether or how Old Opera bookmarks can be directly linked into New Opera versions using Opera Link's services.
