Most people still use one monitor 17-19 inches for their computing display needs. Quality large screen monitors with good resolution such as the Apple 2560x1600 Cinema display still run an unreasonable 1800 USD. A good solution to increase productivity and ease of use is to add 200 USD 19 inch flat monitors to your display. Going from 1 to 2 monitors yields a vast improvement. My workstation consists of a 8 x 19 inch monitor grid powered by 2 x NVIDIA Quadro NVS graphics cards physically supported by 2 x Ergotron DS 100 Quad monitor desk stands for a combined 10.4 million pixel display for around 2700 USD, or 3800 px/USD. Considering the Cinema displays run at 2275 px/USD, my setup, though somewhat excessive, provides good bang per buck.
When using several monitors in Windows, the programme Utramon (torrents) is an indispensable addition. It extends the task bar to every monitor and adds several other simple but effective multiple monitor utilities.