Thanks @l33t4opera.
It's always nice to be reassured that Opera is still on top of things when it comes to security.

According to Opera's Help page you can select the security protocol.
There are extended instructions in the information on certificates.
This would be nice if the features discussed in the Help text exist. However no information is given on finding the settings described and they don't appear to be accessible from the menus.

I can't seem to find such help page on the new Opera 24.

You could select which security protocols you have enabled on the old (12.x) Opera, from the advanced security settings.

Should Opera disable SSL 3?

It seems that this would probably be the wise move.