Throwing my failed side project into the ring as well - Ultralist[1][2] is very similar to todo.txt but has a bigger focus on Due dates. I use it every day.
The CLI portion is fully baked and works great, but the webapp and syncing part never really gained traction.
The CLI portion is fully baked and works great, but the webapp and syncing part never really gained traction.
[1]: https://ultralist.io/
[2]: https://github.com/ultralist/ultralist