I put everything into OmniFocus - my trusted system. Throughout the day I'm constantly hitting my OmniFocus keyboard shortcut to add whatever task just occurred to me to my inbox. It's quick, painless, and lets me stay focused on my work without breaking my train of thought. Later in the day, I'll process my inbox and assign those tasks to projects and contexts. It's your standard GTD workflow.
But one problem I run into is duplicate tasks.
Because I put so much into my task manager - and because I wholeheartedly trust it to keep my data safe and myself reminded at the appropriate time - I often forget what's in there. Frequently, during my weekly review, I'll find that I added a task, forgot it was in there, and then added it again a few days later when it reoccurred to me.
This isn't strictly a problem. Tasks certainly aren't falling through the cracks. If anything, the opposite is true and I'm doubly making sure I remember to do things. But it does bother me. The purpose of a trusted system like OmniFocus is to put your tasks into it so you can get them out of your brain and focus on the work at hand without distraction or anxiety. But the fact that tasks pop back into my head tells me I'm not fully letting them go. Or does it mean that I'm actually forgetting about them so well it's only natural that they reoccur to me?
I'm not sure.
In any case, I don't know of a solution to the problem other than being diligent enough with my weekly reviews so that I maintain a mental model of the tasks in my system. And so I can clean up the duplicates when they invariably happen.