GTD and DIT
I have been using DIT as an adjunct to my GTD for four days. I only finished reading the DIT book on the fourth day. So, any judgement about DIT is highly preliminary.
The fundamental difference between GTD and DIT lies in how "commitments" are understood. In GTD I have faithfully been keeping all of my commitments in my trusted system. I will continue to do this, whether I continue with DIT or not.
The problem that I, and many other contributors to these forums, have found, is that even when I rigidly distinguish my active Projects and NAs from my Someday/Maybes, some of my Projects and NAs sit for months and even years in my trusted system.
GTD stresses capturing everything. The thing is, it's a lot easier to capture all the things I am interested in doing than it is to do all these things.
I do prune my trusted system every week and I constantly delete items or move them to Someday/Maybe, but I still find that there is an imbalance between capturing thoughts as commitments and actually doing what I have committed myself to doing.
What I liked about GTD was that it removed a lot of chaos from my life. It got me focused on the runway--Next Actions--and 10,000 feet--Projects. I had tried Covey and Lakein's top-down approaches and they didn't work for me. The bottoms-up approach of GTD was great.
I have found (admittedly, in only 4 days of practice) that DIT takes a virtue of GTD and makes it even better. GTD got me to focus on the runway. DIT has gotten me to focus even more on the runway. GTD preaches being flexible and relying on intuition in deciding what to do. The problem is that, too often, instead of choosing to do something that would be very helpful, I chose to engage in some kind of worthless displacement activity that would provide short-term pleasure and long-term discomfort. I was much better off than I was pre-GTD, because I was always aware of exactly where I stood with regard to my commitments, and, when the time pressure became too great, I would knuckle down and do what I had to do. But, when the pressure eased, I would "intuitively" spend more time goofing off.
DIT got me to use the day as my planning unit and planning interval. The planning unit is the time period for which a plan is created. The planning interval is the time between planning sessions. I find that GTD is rather indeterminate with respect to the planning unit. I do do Weekly Reviews, since the week is the planning interval. But I never felt that GTD was asking me to create a Weekly Plan, because there is no fixed GTD planning unit because modern worklife is hectic, volatile, and fluid. There were higher-altitude planning units of 2 years, 5 years, etc. But I always felt that the strength of GTD was its treatment of Projects and Next Actions. And GTD does not specify a time for most NAs and Projects other than "as soon as possible."
DIT does have a planning unit. It requires me to create a plan for each day. It urges me to resist modifying that plan as much as I can as I am buffeted by the daily incoming slings and arrows of work. What I have found, somewhat ironically, is that by drilling down to the runway level and planning daily, I am better able to be a long-term hedonist who avoids the immediate, distracting sirens of temptations by binding myself to the mast of my daily plan. If I decide at 8AM what I want to be doing at 10AM, I will make a much better decision (from a long-term perspective) than if I decide at 10AM what I want to do at 10AM.
Don't get me wrong. My self-discipline soared once I became a GTDer. But there was still a lot of room for improvement. By integrating DIT with GTD, by writing a daily plan which I modify only with greatest of reluctance, I am seeing that improvement.