I have 2 monitors at work, and the other 2 engineers liked it so much they copied. The other two do a lot of CAD work, and with identical monitors, can stretch the active window onto two monitors for an (almost) seamless view that is effectively much larger with two 19"-ers than with a single 22".
For myself, I can edit word documents (right screen current version, left contains changes), or search an excel workbook and verify drawings on the other.
My setup has a 19" LCD almost centered, and a 19" CRT to the right. So most work is done facing almost straight ahead. Neck/muscle strain has never been a problem for me because I can never work for an hour without interruptions.