I was searching the net and came across this post in the Atomic Forums.
I had two thoughts - the first is that once you go above 19in screens, the width of the screens becomes quite difficult to scan your eyes across... you almost have to turn your head to see the edges of the screens, and this becomes quite annoying after a while.
My 2 Dell 20in screens are running in portrait so that I can actually use them both at once without having to strain my neck each time.
I am aiming to add a third screen though - and unlike the user in the forum thread - its not for watching movies.
Now it may seem overkill - I'm sure you can see the usage of 2 screens... The 1st for working, the 2nd for source material that you may be working from; a word doc, a pdf, a webpage, a movie that you are reviewing etc...
But this third screen? What is it for...
Well, it is for tracking and meta-analysis.
I have been doing a lot of work with the E-myth concept and they strongly recommend tracking all the tasks you do during the day... The problem is, that even with a nice spreadsheet for doing this - as soon as the window disappears under my other work --- it gets forgotten about!! And then, my tracking falls apart and I can't see how my work is going for that day...
So the third monitor plays a crucial role for you and your employees - allowing them to accurately track their work each day, so that they can have the overview to improve their flow and productivity while at work!