The time tracking with task and sub-task could be enhanced.
For example, as soon as you enter a sub-task for a task, to original estimate of the parent issue may be the sum of all his sub-task. The display progress bar of a task could also be enhanced with that instead of a ratio of resolve/total sub-task. For example, a task advancement is 66% if 2 of 3 sub-tasks are resolved even if the third task is estimated to take 10 times the time others.