I just want to have a clutter-free desk, and my computer being open doesn't really help then. It takes up a lot of space and even though I have the space (I have a large L-shaped desk) I just want to work at a clean and empty desk.
That said, if I need to use multiple "windows" I just add a Mission Control desktop. Unless you want to look at two things at once you really don't need to have two displays nowadays.
I cleaned up my desk just now (yay for cable management!) so here's a pic to stay OT.
I'd recommend the TwelveSouth BookArc and BassJump to everyone that uses a MacBook. They're absolutely great accessoires.
Very clean, looks great!
It definitely does look better, but I've been using dual monitors for years and just love it too much. Like when writing a business letter or a paper or something you can have notes or research open on one screen, and the paper itself on another.
That said, I saw one of these at a MicroCenter the other day and thought they were too cool;
http://www.hengedocks.com
Basically all of the connectors for your cables get stuffed inside it, and you just slide the MacBook/Pro/Air into it and 'dock' it. With the mid-2012 Pro (and most other models) it would be pretty cool, because ALL of the cables are on one side. Could really get a clean setup that way.
Cable management is a problem on my desk! I'll admit it