[cellis]

i can only speak to having 3.

https://dl.getdropbox.com/u/163594/IMG_0077.png

I like it quite a bit...it helps especially when you have 3, 4,5 IDEs open and don't feel like constantly resizing/maximizing them.

[wheels]

The problem that I notice on two monitors already is that I really need focus-follows-mind. I too often forget which monitor / app has the input focus and start typing away in the other.