This should be titled, "two big screens aren't better that one big screen." I've had multiple desktops with two 21" CRTs, back when that made you a fancy boy, and had considerable improvement in workflow from it. Now, with my 27" Thunderbolt monitor, I can't imagine the frustration of having to turn my head instead of move my eye to change my mind's focus.

This transition was after having done most of my development on a 15" laptop, and re-learning how to be productive without distractions... everyone's mileage will of course vary, so blanket statements are worthless.