I don't know about the Opera version of tabs but in Mozilla 0.9.3 I used tabs because the new window delay was ~2s due to excessive XUL overlays and I installed

I don't know about the Opera version of tabs but in Mozilla 0.9.3 I used tabs because the new window delay was ~2s due to excessive XUL overlays and I installed the save tabs extension because the browser crashed every 2 hours or so and I wanted to keep my tabs.