I could never do that. I use 3 monitors (if you count the laptop) and I'm way more productive with it. I have low-priority windows that I need to have opened (a terminal, a console log with 3 tabs of its own, simulator window) and that is a mess to handle if I have to actually switch between them. Virtual desktops help a bit but still cause a little strain every time I have to switch from one context (development or checking the source) to another (testing a mobile app and checking the log).

I thought so, then downsized to just one monitor, and that was pretty great. When I move around, working on just on the laptop doesn't really impact my productivity that much, unless I'm in a deep debugging session, but I think a larger screen will help with that (I use a 13" Retina right now)

I did that as well! The outcome was an improved way of working.