I met a guy who likes Opera but would prefer to use windows instead of tabs. The more technical name for this is SDI (Single Document Interface) opposed to MDI (Multiple Document Interface) or TDI (Tabbed Document Interface, which is kind of a crippled MDI).
As Opera is astonishing customizable it is pretty easy to make Opera behave like a SDI application. But it requires to change several settings. During my research I couldn't find a somehow complete guide for this. So here is my comprehensive description to make Opera SDI-like.
Update: Shoust made a nice Custom Button that toggles between SDI and MDI, which very easily changes the settings for Open windows instead of tabs, tab bar and Middle click option (background window / background tab):
button …