Adding my voice to the pile here. This change added unnecessary work for the end user. The previous position was right beside the tabs and opening old tabs only required one click rather than navigating through a menu to access another menu. Accessing the old tabs menu was such a smooth processes that it became something the user could do without thinking about it. That's a goal any UI developer hopes to achieve. Why on earth would you make it more difficult to access such a basic and perfectly implemented feature?
I've disabled the flag for this change but this is yet another baffling change for change's sake that Opera has made, the only thing keeping me here at this point is the Speed Dial.