I just tried to switch from chrome to opera, hoping that it skips some of the more dubious google choices like forcing on the desktop notification in the newer builds.
However, the crippled search engine functionality is a show stopper I'm sorry to say. I'm not ranting, I respect opera is using google's engine and probably has to contribute something back like the hardcoded "g" bang and the prevention of the removal of the google engine even after deleting "default_partner_content.json".
But for crying out loud, not being able to set my own engine to default is so annoying I'm going right back to chrome. I hope the "temporary" situation doesn't last longer than the half year by now, I don't know if you realize that forcing this choice on users might hurt opera more than you realize and a re-negotiation with google might be feasible.
Thanks for keeping opera alive anyway, maybe I'll have another look when this is resolved.
The option to set a custom search engine as default was (temporarily) removed to combat malware overriding user settings and directing all searches to malicious third-party sites. Its an unfortunate situation.