I'm checking out Opera after using Firefox for quite some time. Overall I am really liking Opera.
One tab function Firefox has that Opera seemingly doesn't is the ability to "lock" a tab which prevents it from navigating to a different URL (as opposed to pinning or protecting a tab to keep it from closing).
I believe this functionality in FFx is part of Tab Mix Plus, which doesn't seem to have an extension for Opera.
Is there anything else out there?