How many monitors does your gaming PC have?

How many monitors are usually connected to your gaming computer?

What do you think are some of the better uses of multi-monitor setups in games? What potential uses would you like to see?

Are multi-monitor setups particularly hard on GPUs aside from the increase in the number of pixels?

How well does UE4 handle multi-monitor setups? Anything in particular to watch out for or to take advantage of? By this, I mean both for developing UE4 games and playing them.