I've been using Taskwarrior for a few weeks as my primary task manager, and I have to say it's a beautiful extension of the principles of Todo.[txt/sh]. The only thing missing for me is the ability to apply modifications to filters instead of needing to use explicit task ID lists. For example:

  task proj:Foo due:tomorrow

Instead of:

  task 1,2,3,7,10-12 due:tomorrow.

For oh-my-zsh users, I've got an open pull request for adding a Taskwarrior autocompletion plugin:

https://github.com/robbyrussell/oh-my-zsh/pull/370

The intelligent completion lowers the barrier to task entry even further.

You may also want to try using a combination of Taskwarrior's shell mode and rlwrap, which has become my main usage method:

  `alias ts=rlwrap -i -r -C task task shell`

Combine this with a drop-down terminal like Guake or tilda, and you've got text-based-tasklist-anywhere nirvana.