Task Coach seems to offer everything I ever might need (even in the future) but lacks one essential feature: Show the complete sum of all efforts of a task and its subtasks in a simple way.
The effort window sums up per month at maximum. And I have to select each relevant task, to see its sum for a range of time there.
An additional column in the task window besides "budget/effort" named something like "budget/complete effort" or "effort sum" and showing the effort of each task including its subtasks would simplify my freelancer life enormously ... ;-)
You can get the totals for "budget", "time spent", etc in the Tasks Viewer by collapsing the relevant sub-tasks