I use PGE todo, so I'll write what I miss in it.

1. subtasks - if I have a task "write program", then I want to add subtasks "design program", "code program", "test program", etc. For me 5 levels will be enough. E.g. tree structure.

2. Time. How much time should be spend for task, how much time is already spent.

3. Move complete tasks to special folder instead of deketing it. So it will not disturb, and it will be possible to review them.