I am seriously enraged by this action. Removing this shortcut without even allowing it to be optionally turned back on is a grave mistake. This was THE core feature that made me pick opera above other available browsers. Also, it was the main reason I recommended it to my friends and family. I can not comprehend the logic of "not enough people using it" to be the sole argument for removal of this feature. A lot of features are not used on a daily basis by the average Joe, yet somehow you decided to get rid of this particular tool.
As for staying on previous versions of the browser - you gotta realise that guys who decide not to update the browser are going to be at risk for safety, because alongside questionable development choices every new browser version patches the possible security gaps. That means whether someone was to create a comparison of the browser's safety, these users could prove your product to be inferior.
Opera, please, bring back the instant search box as a optional feature and stop forcing me instagram feed on my favorite and most important tool every time you update.
Sincerely,
Jake