I have found a rather simple work-around to remedy the situation that works in both Opera and FF.
Go to google.com, and right-click in the search field; Click "Create search..." in that menu, that will bring up a "Search Engine" dialog. Input the following in that dialog: Name = google, Keyword = google, Address = already filled in automatically. Also check the boxes for "Use as default search engine," and "Use as Speed Dial search engine" ... Done. All functionality returned. This 'fix' will have to be done for each user on the system. The LinuxMint Google search will still available as an option when you search from that field if you choose Google with an uppercase G
Download the Google tool bar at http://toolbar.google.com/T6/intl/en/index.html
and choose to download and install said tool bar. This is a per-user thing and does not require administrator privileges. Once installed, you can click on the "options" button in the tool bar to edit and configure functionalities and best of all, under layouts choose: "Replace Firefox search box and hide Google toolbar."
That will at least make it look like the original FF search box, but with more and better features, such as, but not limited to, searched text highlighting. This is the only fix I have found that actually works. From what I can tell it's a very simple add-on that won't weight the computer down with un-needed code or privacy intrusion. This fix as well will need to be done on a per-user basis for any user who wants it.
No disrespect to the LM team, I really love the distro and hope you all do well in your endeavors, including making money like this, but it just seems too restrictive for some of us users I suppose.