Hello,

Many of the projects in our life are sequential by it's nature, that is you can not complete second action until first has been completed.

As a trivial example:
1) Wait for movie to get downloaded.
2) Watch it.
I just cannot watch it until I have it.

It's pretty annoying to have lots of actions showing up that can not be dealt with any time soon. That's direct violation of one of the core GTD principles, I believe.

My proposal is (when sequential mode has been selected):
Items should be hidden until all previous won't be done. That requires users to be able to set order of tasks (by dragging them and/or via hotkeys).
Of course, current "Parallel" mode of projects should stay available for selection.

Nirvanahq has great implementation of this feature if you are looking for an example.

Thanks,
Alexey.