At work I have three monitors on my desk – one 20″ wide-screen and two 17″ regular monitors. At home I have just two somewhat mismatched 17″ monitors. Admittedly, in both cases all the monitors are attached to different computers, but using Synergy they respond to the same mouse and keyboard.
I do a lot of programming using Eclipse, for example, and I have found that the widescreen monitor is considerably more effective than the old 4×3 style. The extra width gives room for a variety of toolbars and navigation panels at the side of the screen. I have tried using multiple monitors on a single computer but have never found a satisfactory way to use them. Splitting a single desktop always seems to result in windows with a big opaque bar down the middle, which I hate, and makes the “full screen” window button effectively useless. So far I have not found any desktop settings which support the option of “full screen” filling the display the window is currently displayed on. Perhaps I should try harder!
It’s sometimes more difficult to justify getting a bigger monitor for home development, than for one used at work for paying customers, though.