If JustTodoIt is just too simple for you, GeeTeeDee might suit your need better. This Windows application lets you group tasks, move tasks between lists and attaching notes and due dates. The interface is pretty clean and nice and it has a compact mode to hide the left panel.
Adding a new task is as easy as clicking the New button or double-clicking on the checklist area. Want to keep adding tasks without having to move your fingers from keyboard to mouse? Press Enter, and then Shift + Enter.
Unlike JustTodoIt that deletes a marked task, GeeTeeDee does not. Any checked task will be marked in grey and staying in the list until you press Delete button on your keyboard.
Additionally, you can also see the number of tasks of each list directly for both overdue and active tasks.
Another thing that you might like from it is that overdue tasks are marked in red.
GeeTeeDee works for Windows, Mac and Linux and available for download here.