I had the same. I installed it and realised that it had imported my Chrome bookmarks. I didn't purposely choose that, so was pretty annoyed, but thought that maybe I'd missed a check box. When I realised that it had made itself my default too, I uninstalled it.

I reinstalled it a while back to try again and to test a website I was making, and after one update I launched it and it played a really loud sound. It was late at night and my kid was in bed in the room above me. Because I wasn't expecting any sound, never mind anything that loud, I panicked and didn't turn the volume down in time.

After I got my kid back to sleep I uninstalled Opera permanently.