Multi-Monitor Productivity

Does having more then on computer monitor increase productivity? Some research I did on the subject found: http://research.microsoft.com/displayArticle.aspx?id=433 http://lifehacker.com/software/dual-monitor/dual-monitors-increase-productivity-168488.php http://www.matrox.com/graphics/en/gxm/products/dh2go/home.php Vedors Hardware http://digitaltigers.com/index.shtml?gclid=CJv0uqGo6I8CFR7qYAodNR8dkA http://www.9xmedia.com Software http://www.mediachance.com/free/multimon.htm http://www.realtimesoft.com/ultramon Hardware/Software Combo http://www.maxivista.com