Working on more than one monitor is becoming a standard. Especially for software developers and designers. It really helps to focus on the things we're currently working on. The less important stuff is usually moved to the second (or even third) screen. Web developers will also find it great to have a website on the first screen and code editor (or debugger) on the second one.
Personally, I used to find working on multiple monitors a little bit confusing. I love the huge space, that's for sure. However, there was always a problem with too heavy brightness when two displays are on. Sometimes I used to turn the second one off, so the brightness in peripheral vision was not that distracting. Unfortunately, it caused the windows from that screen move to the main monitor – quite understandable but in this case it was a real nuisance. As it turned out, I'm not the only one who has such issues with multiple displays.
One day I decided to make an app that will overcome this problem. Our team got down to work and finally we did it. The app works pretty well. Basically, it follows my cursor position. By default, main monitor is bright and side monitors are dimmed (I can set the dim level and choose which monitors are dimmed, of course). When I need something from outside the main screen, I just move cursor to the side display and it brightens up immediately. When I move the cursor away, the side screen gets dark again. The whole process looks smooth, non-distracting and natural.
I don't dim my side monitors anymore. Definitely, I don't turn them off. I use ScreenFocus instead.