I had 3 for a while, then went back to two, and am quite happy with that.
There were no problems having the third one, but it took up enough real estate and a friend of mine had me build a computer, but he only had a 15" CRT display, so I gave him a 32" HDTV flat-screen.
But, two work well for me, and with screen sets, I am quite content.
Bob Bone