It would be great to be able to have users log hours for a particular task. You could then show a progress bar within the gant of the task showing the progress or hours used.

E.g. A task has 5 days with 8 hours each day. 3 Days into the schedule a person logs 24 hours work on a task. If a user logs more hours than allocated, you could make the gant turn red to indicate it has gone over budget.

You can see something similar with fTrack.