[berkes]

Putting often used controls (tabs, docs, menus, etc) across the long side has a solid argument going for it too, though: your mouse pointer is almost always closer to one of the long sides.

Also, if vertical screen estate is a concern, just turn your monitor 90° A lot of professionals working with paper sized documents (legal, bookkeeping, administration) do this.

As a software engineer, I've tried it, but I prefer splitting windows (tiling, or panes or such) horizontally. So my estate is limited in width more than in height.