1. open-source. 2. One command away from my editor(I only use desktop for taking notes), also synced to my dropbox in case. 3. Amazing extensibility with plugins and custom scripts. Eg: bugwarrior + pomodoro(using Timewarrior, I've used this a lot when freelancing, not so much now) + some custom scripts. 4. Journaling - custom generated template of what I need to records/daily tasks etc. 5. Viewports in taskwiki are amazing, eg: for any project related notes I can do write `# Task | project:Pro1 and +PENDING` to list pending tasks in Pro1, you can also configure to use tags like development, bug reports etc.
I couldn't find another tool that is as extensible. The downside is you need to dedicate a weekend to understanding and setup!