For those who use the GTD (Getting Things Done) system or have used it in the past, what are some areas where GTD is weak and might need improvement?
In my opinion GTD lacks as a whole-stack system because it's much more of a middleman, gluing the higher levels to the trenches in a brilliant way, but failing to cover the extremes themselves.
By the trenches, I mean actually executing tasks. The most GTD can offer is the 2-minute rule for tasks that can be done on the spot, but for tasks taking longer than that, look for The Pomodoro Technique or similar workflow management methods. It's helpful to break it up into work chunks spaced with breaks, and it uses the concept of timeboxing, which is to define a constraint during which you work on the task, no more and no less than the time box.
Then you also have habits, recurring tasks and other activities that aren't due but require some frequency, as well as tasks with a set due date themselves (though you have the Tickler file, it's not quite efficient as a task lisk).
Habits naturally lead to goals, being the why you are doing such things as habits (which are really just any action compounded over time) or any other tasks. GTD has absolutely no way to go above the project level, so I consider goalsetting it's biggest weakness. And when you go above goals, you have your long-term vision, and your purpose on Earth and thus the guiding principles (values) of your life. There are great many articles that cover those--though I know of no established methodology and would love to hear of one. Once you have these parts down it's easy to then link up goals to your GTD projects.
While GTD may come across to some as the workaholic manager's productivity system, I disagree with this view. I think it can be a wonderful tool to map out the current possible paths to your life and then prioritize, with periodic reviews. The key in GTD is that you're ready to pivot if necessary--all the information is on the table, not in your head.
I believe that GTD makes you lose track of what matters in your life and puts too much emphasis on "productivity" (doing as much as possible) over effectiveness (doing the right thing).
I moved to the Seven Habits of Highly Effective People, using some of the rules from GTD, and never looked back.
UPDATE: To answer @Muz, I like the fact that 7 habits encourages me to schedule time for important stuff (gives you a week view), rather than going from one action to the next.
But I kept several things from GTD: dumping everything that is in my mind into lists of tasks, the 2 min rule, and how to make a task actionable by using very specific next actions.
I didn't want to list my web app here to not appear as spammy but I think the web app describes well what I mean by mixing 7 habits and GTD to stay on top of what matters. Check out WEEK PLAN: http://weekplan.net
Found an interesting article on where GTD fails.
In short, it categorizes everything as next actions, that is, a thing to do next, like "get Amy's number" or "buy a pencil".
However, it fails when it comes to huge goals, such as "write a book". Writing a book can not be broken down into actions as "Write chapter 1", "Write chapter 2".
On the other hand, GTD helps in reminders of things you need to write your book, such as "Introduce character A", "Write out argument scene between Andrew and Malik". Breaking down tasks into next actions has always been a powerful tool from programming, in my opinion. But there's a limit to how far some things can be broken down.
Also, as stated in the Mastery book quoted in the article, mastering something requires going through a painful learning phase and a creative experimentation phase. By breaking things down into 'next actions', you may get a mastery of how to break difficult tasks down into 'next actions', but at the cost of actually mastering that task. So if you actually manage to break down writing into a series of next actions, you won't actually master the art of book writing, but instead master the art of splitting and assembling lots of segmented portions into a book. While that can be a positive thing by itself, it may not be what you are looking for.
I just saw an article about this on Cal newport's Blog. The basic point is that it's good for the mundane and for completely dehumanizing everything you're doing. It lacks prioritization. It is good for getting the litle things done and remembering everything you put into the system. It is not good for important things or for more thoughtful things. Read the article, I can't write as well as he does.