I just set up my new dual-display system here. The cost of monitors is so low now that you can have this sort of setup without spending too much money.
Today (in the supermarket!) I bought a 22" Dell widescreen and I'm using it with my current Sony 19". Now that I've tested the concept, I'm going to buy another Dell so the two I'm using are the same.
Within the first minute of using my new dual-display setup I can already see how much less opening and closing of windows I'm going to have to do during my working day, and how much easier it's going to be to work with all my 'stuff'.
It's a bit like when you go from a small computer desk to much bigger one - there's just so much more room to keep all your work neatly in front of you, without it all getting tangled up.
One weird thing is getting used to your mouse pointer not banging off the right side of the screen when you're whizzing over to the scroll bar or close button - the pointer zooms of the edge and appears on the other screen.
I can highly recommend this way of working to people who have been thinking about doing it.