People may scoff at the relatively puny 20" and 17" sizes, but I also regularly go into a different office and use a Dell 30" with my laptop.
Dual 30" monitors would seem like a great solution, but my problem is that they don't have any curve to them. They are actually too big!
With a group of smaller monitors, you can angle them so they form a curved array, and that makes viewing more comfortable for me. As I swivel in my chair, I'm facing one of my screens pretty much square-on.
If I was to start over, I'd probably go for three 24" monitors, turned sideways.
But today I see that Alienware is promising to ship a curved 42" monitor. Something I've been waiting for. I think curved monitors are the way of the future for desktop screens.
Now I can wait until those curved LED or LCD monitors come out, and come down in price to about $1400. Lest you forget, Alienware is actually owned by Dell these days.