You young schmucks should listen up!
When you hit 40-50 years old your eyes will seize up and you'll be able to focus at exactly one distance. You get glasses, then you have a choice of distance (TV or driving) and reading (books or monitors) as well as whatever your eyes can do by themselves.
One thing you'll notice is that at the closer distances, the focal depth is very small - it makes a big difference if the monitor is 40cm away or 50cm - at one you can focus. At the other you can't. Brutal as that.
Now sit down at a 75cm (30") widescreen monitor and WTF - if you can focus at the centre, you can't focus at the edge. Unless, of course you sit 2m away or more.
That's why I'm sitting exactly 45cm from my good old 43cm (17") diagonal 1920x1440 Philips 107P4 CRT monitor. It beats the crap out of the Dell 2001FP 51cm (20") 1600x1200 monitor at work both in the quality of the image, the number of vertical lines of code in emacs and my ability to focus on it. When they offered me an upgrade to a rootin tootin 27" wide-screen, I tried it and sent it back - just couldn't focus all the way to the edges.
If any monitor manufacturers are listening here, WE WANT VERTICAL PIXELS _AND_ A NICE COMPACT FORMFACTOR - around 43cm, thank you very much!! I'm not talking a small demographic here - it's the baby boomers!!