Another technology that has come down in price recently is the cost to setup your system with dual monitors.
You may want to use a dual monitor system for a while before you pull the trigger on this technology.
When I am looking at a computer screen, it takes my eyes a lot of time to focus in and gather the information in front of me. When I had dual monitors setup, it was nice to have all of the extra screen space. With my email open on one screen and Internet explorer on the other it was nice to not have to switch between applications when I wanted to go between the two. However, I found that my eyes had to work twice as hard to focus from one screen to the next plus I had to move my head slightly to view the other monitor. Even with both screens being the same size and resolution.
The solution that has worked best for me, is one large monitor. Sure, it doesn't look as fancy but it has saved me the strain of having to look back and forth all day long. I also think that the price of one large monitor is comparable to having two smaller ones.
My advice? Test the technology for yourself before you choose to buy. If you have a laptop this may be easy for you to do depending on the setup of your system. Try plugging in a monitor to the external monitor port on your laptop. You can then change the video display settings for your laptop to show dual screens (one screen is your external monitor, the second is the LCD screen attached to your laptop). Try it out for a week and see if it is benefit for you.