I wish I could get away with using one screen but alas I just couldn't handle it after all these years with two. My problem is that I have my monitors either side of the main screen (they'd be way too far apart if they were either side of both screens) and this means my second screen is way off to the right and angled inwards, which isn't too bad I suppose but it does make for more neck swiveling.
I even thought about installing the second screen above the first one, but I think that would feel incoherent when dragging the cursor between screens, and besides I have a friend who tried a setup like that and ended up having to have physiotherapy on his neck.