I just finished reading Do It Tomorrow and think it is a fine book. I do think it will appeal more to the self employed in my opinion. Specifically those whho have sort of well known business missions or life goals and less input from a boss.
The idea of a closed list is central to the book as well as a daily task diary and not doing anything you do not write down. I tried this for a few days and it is eye opening to see what you think you can get done versus what you actually get done. The idea of a closed list for daily actions makes sense to me, but I actually like open lists of projects and someday/maybes because I like to see things I could be doing and track them. I am more concerned about forgetting a good idea or something I might want to do than having too much on a list. I personally think GTD covers the idea of a daily task list with its use of the calendar. If something has to be done by a certain date, according to GTD it is put on a calendar.
For me I like to see lists of projects and waiting fors on lists it just makes sense to me, versus having to flip through many pages. But, I can see how the daily task list can lead to more focus and productivity.
At this point after implementing GTD first, I can not see a method working for me that does not attempt to record all of my open loops and ideas on lists. The idea of viewing the landscape on a few pages just makes sense to me.
I do think there are ideas in both methods that could meld well together.