I know, opinions are split on this one, but I have been working with two monitors ever since I started working as a freelancer full-time, and I wouldn’t want it any other way.
First I used an additional monitor to the one on my laptop, then, when I had my desktop PC custom-build, I bought a larger monitor (22″) as main one and kept the other, smaller one (17″) as extra. I have them set up so that the extra monitor is to the right of the main one.
I use the larger one as main monitor, because it lets me view two documents next to each other, e.g. two text documents or a text document and a pdf, when I am proofreading, checking formatting etc. It also offers lots of space, i.e. information (TM view, termbank view etc.), when I work with my translation tools, which makes things a lot easier and faster in my opinion.
The smaller monitor to the right is my reference monitor. Here I have my web browser, my dictionaries and any reference documents open, so I don’t have to constantly switch between programs while translating. Another plus is that I can write e-mails on the main computer and have any documents, websites etc. I might need to peruse or reference to in the mail open on the second monitor, again making switching back and forth unnecessary.
I cannot imagine working with only one monitor – regardless how large – anymore, and have a hard time adjusting whenever I have to work on my laptop and just that one monitor. A colleague of mine is even thinking about adding a third monitor, but aside from the fact that I’m not sure how to connect a third monitor to the computer, I’m not sure what I would use it for. I’ll probably buy a larger monitor in the future and then use my current main monitor as second one, but then I’d probably toss out the smallest one. Three would be just too much – and besides, I would need a bigger desk, too – again! – , so, no, no third monitor for me (for now).