For me, monitor size is dependent on real estate needs. If I'm doing work that requires a lot of high-res visuals I can make use of two monitors; but if I'm working with plain text, an 80x25 character display is usually fine. I do not generally use monitor space to view things I am not working on - at most, I'll have one chat window going. In the past I felt an improvement from more monitors, but now I suspect that they are mostly band-aids for a lack of concentration.

I generally recommend to people to get smaller sized laptops because the lower bulk will help to absorb bumps and drops.