I like using multiple monitors largely for the aforementioned reason that you can have code on one screen and documentation / web page output / forum discussion

I like using multiple monitors largely for the aforementioned reason that you can have code on one screen and documentation / web page output / forum discussions / IRC on another. In my opinion it is far easier to context switch by simply looking left and right as opposed to continuously switching between windows being in the foreground or background. I also think it's faster to look around than alt-tab, plus you don't lose your spot on the page you're reading / document you're writing as easily when compared to having the text completely disappear from view after switching window focus on a single monitor setup.