I have long been a fan of dual monitors for software development. Recently though I started working with a single 30" monitor and I like it much more than the dual monitor configuration. I really like being able to have two things open side by side, an IDE window and a browser window, Xcode and the iPhone Simulator, etc. You just can't do this on a single monitor smaller than 30" but at this size and resolution I find it's easy to fit two windows side by side. For me it has the same benefits as dual monitors but also allows for a simpler hardware setup. I also end up spending some days using my laptop and some using my desktop and it's very convenient to be able to use the same display setup with both. This was something that was not workable with the dual monitors as the laptop doesn't have a great way to support two external displays.