I don't often run things full-screen. I like windows, they give you virtual screen real-estate at the click of a mouse.

Example: Right now I have a project with a main application, a launch agent, and a framework. I can fit 3 columns of text with the font at a size I can easily read across one window in Xcode. I generally work for a period of time in one of the app/agent/framework areas, so I have 3 Xcode windows open on the same project, each having ~90% of the screen with a little overlap.

Sometimes I'll have another similar window, for out-of-context work. If I'm creating a class, and suddenly realise I want to re-factor some other class to make it work, I'll open another window (again with the 3 columns) for the re-factor work, leaving the state of where I was ready to come back to at the click of a mouse.

I personally find it easier to mouse-click to change context than any other way, so keeping the screen 'mostly' used works better for me.