I really agree with this post. It's something that I have been offhand talking about for some time, now it turns out that others are beating me to the punch. I'm totally down with this. Recently I started checking the "automatically hide and show the dock" option in System Preferences. I started doing this because I wanted more screen real estate to deal with photos, then I noticed that I could concentrate better when I couldn't see all of those little icons tempting me to switch tasks.
This is one reason that smartphone OS's are sometimes better for reading or working on, they aren't able to distract you as completely as a desktop OS GUI can. On iOS, Android, WebOS, and others once you start a program, that program takes up the entire screen. You have to make a real effort in order to get to another task. Sometimes a trivial effort, such as hitting the home button or pulling up the card interface, but a conscious effort nonetheless.
When I can't see the dock, all I have is the menu bar above me, which is far less distracting than the dock.
Now, this doesn't mean that is enough for me. I've tried Writeroom and loved it. Writing full screen is awesome, and really gets the creative juices flowing. Computers are distraction boxes, and anything that can lessen that is a Good Idea.
I do have one set of features in my ideal version of these sorts of attention controlling programs (human task managers? I think I'll go with that): the ability to define tasks and have the program allow you only what you need for those tasks.
Example: I'm going to write a paper!
Things that I need: Websites to get facts from, a word processor, a music player.
At that point, I would like to be able to explicitly define what websites I am not allowed to go to (facebook, flickr, google reader, etc.), or perhaps ones that I can go to. Then I want to be able to define a schedule for this. An hour of work, and then the program nags me to go do something else. I could tell it "I'm on a roll here, stop" and continue working. Or perhaps it could track my activity and force me to take a break when I've been staring at a word document for too long. I want this thing to babysit me through writing a paper because, except on breaks, I really don't need to be visiting facebook or reading about how Portal was made.