When you click on the "hours spent" link in the task details, you will see the text box right below the field for entering hours. You can use this text box to specify what exactly you have done so far.
In the time report, you will see not only a list of time entries for each task, but also have a clue about what the time was spent on. This way, you can always provide your clients with a thorough report of what you are billing them for and ask the same from your contractors.
More new handy features are on their way to come before Christmas! In the meantime, if you have ideas of what can make you more productive, please let us know at our voting forum.