Mission Control on OS X on a laptop is also a huge improvement over overlapping windows. Swiping between full-screen apps becomes second nature very quickly.

""Perhaps even more than adding an extra display, which is often said to be the cheapest way to improve productivity.""

And which can also be a way to decrease productivity, with distractions etc. I am more productive on a smaller screen laptop than I am on a 2 screen set or even one larger (21, 27") screen. Mainly because it helps to focus on the task at hand.

We also didn't have 2 large monitors to each workstation back in the day, and somehow we did fine. Spoiled much?

We used to program with punch cards... so yeah we're spoiled and damn happy about it.

Evoking punch cards?

As a programmer, you must know about diminishing returns, right?

Nevermind diminishing returns, how about full circle? Eventually all of this abstraction will become so hard (and buggy) to maintain that we'll go back to using punch cards.

Personally, I get more work done at the office where I have two screens. When I'm at home on my laptop, I notice a difference in productivity. It's not a huge difference, but it's noticeable enough for me to want to buy a nice 27" the next paycheck.

As someone that's easily distracted I've found Lion's full-screen support is quite the blessing if you're trying to focus on getting things done.