Hi,
There are a few features that would improve my experience with doit.im:

* Sequential tasks in projects:
An option to make the tasks in a project sequential, so that only one of the tasks appears in the next actions at a time (or kanaban style, so I choose which ones are active).

* Start time:
Add a start date to a task, so that it is in hold state till the start date arrives.
In hold state, it will not show in the next actions or the schedule (even if it has a due date).
Note, that start date should be to be repeated in recurring tasks, hiding it till an amount of time before the due date.

* Add comments to projects (similar to tasks).

* Update importance of tasks using the right click context menu.
If I'm not mistaken, there is currently no way to change the importance of a task without editing the task (one by one...).

* Recurring tasks by completion date.
Sometimes a task is to be repeated a certain amount of time after it was completed (i.e. I would like to be reminded about the task again, a month after I complete it).

* Subprojects or "real" subtasks.
Sometimes a task within a project must be broken into several tasks.
These are real tasks, that I want to see in the smart lists (next/waiting etc.), so the current subtasks list in the tasks is not a solution for this case.

* Later.
Sometimes tasks are something in between someday/maybe and next. They are to be done, but are waiting to be prioritized asap.
In projects, I deactivate projects so they are in "someday" state.
This later state would be useful there as well.

* Reference material.
Evernote and comments are nice, but it means I need a third party if I have a PDF I need as reference for the project. Why not add the option to upload reference material to tasks/projects?
To this end how about adding a "reference" state to tasks, turning it into reference material, not showing up in the smart lists, but rather in the reference material of projects.