Guys/gals, do not trust Opera when it tells you that it will reset without losing stuff. I just discovered that Opera had lost all of my extensions. And I really can't remember which extensions I had, or where I had found them.
When using the Update and Recovery > Recover feature, it says "If the browser isn't running well, resetting to a default state might help. You can choose to preserve your personal data and only reset settings or to perform a fully fresh reinstall." Well, I think it should be made clearer to the user that Opera will delete all the extensions (not simply disable them all).
In fact, the dialog says: "This will revert your search engine to its default, remove pinned tabs, and reset browser settings. It will also disable all extensions and clear temporary data, like cookies. Your bookmarks, history, and saved passwords will not be cleared." But it doesn't just disable your extensions -- it deletes them (and all of their settings) from your hard drive.
(My bookmarks and my passwords are still intact, so no, I did not accidentally choose the second option.)