Question: do you use horizontal or vertical monitors? I've gotten so used to vertical for code and for web pages I'm developing with Firebug that I can't imagine preferring horizontal for writing code. But I've seen few others running that way. Am I crazy?

I use 4 monitors. The 4th one is great for not having to manage IM window positions or look at them when I'm working, since it's outside my normal visual focus, while letting people still contact me asynchronously for things they need from me.