Plaintext Productivity
Whatever system I have (tried to) used over time, I've run into the following challenges:1. how to deal with old tasks (are they relevant anymore? should they be removed?). 
2. connecting tasks to their related source and needed information to actFor the former, the accumulation of old stuff has consistently led to less and less usage of the system and as a result to a continuously decreasing trust in that system. Adopting a new solution has given the feeling of a better system with better chances to success; but it has mainly been about having a (temporarily) new clean inbox.