He says this about why a company where he worked decided not to use timesheets when they went to a Critical Chain Project Management system (CCPM):
The root reason that we decided to not use time sheets for our CCPM implementation is that they are not consistent with the principles of CCPM. CCPM is interested in successful execution of the overall project: Are we working on the right things? How much longer on that task? Is Jan ready to start when Joe finishes? Time cards are focused on execution of individual tasks: Did you start "on time?" Did you finish within the allotted time? This information seems very useful for billing and managing individuals, but not the success of a project. The meaning of starting something on time is almost irrelevant in real project environments where the initial duration estimates are estimates and not carved in stone. It doesn't particularly matter if Jane takes longer than expected as long as the team sees how that will impact their subsequent work and what can be done to recover excess buffer incursions.
Jack mentions that CCPM is interested in things like "How much longer on that task?" and "Is Jan ready to start when Joe finishes?" and I agree that these are key elements of any PM system BUT (there is always a but!) how do you know "how much longer" and "...when joe finishes" without a way of finding out? A timesheet is the way the PM asks 50 resources when they will be finished. Sure along the way it also asks when they started and how much time they have spent doing it but that is also useful info in ANY system CPM, CCPM or otherwise.
Jack also talks about it not mattering if "...Jane takes longer than expected as long as the team sees how that will impact their subsequent work..." But how does the team know that Jane is taking longer? How does the team know the impact on the original plan unless the PM gets this new info from somewhere and then updates the project plan? The timesheet serves this purpose.
I hope that I did not make it seem like a timesheet was JUST about collecting hours for billing. If I did then shame on me. A timesheet should be about more than just collecting up hours worked or "Did Bill start on time?" Sure it gets those things and uses them for things like billing and also for examining WHY Bill did not s tart on time. But that is OK because seeing (in the post mortem) that Bill did not start on time is a good thing. Did he not start on time because he did not have what he needed? Maybe there was a flaw in the project that we can notice because we were able to look at things like Start Variance and see that Bill was delayed. Was he late in starting because he sucks as a resource? Maybe he needs to be trained. :-) My point is that Timesheets are about WAY, WAY, WAY more than just collecting the hours spent doing something. They are about a method of communicating in a very structured way about some very precise info: When did you start, how much did you do and (here is the big one for me) how much do you have left to do? I think this is the key for CCPM as Jack mentions it in his article. But it is important for CPM too! :-) All PMs need to have a solid, updated estimate of how much longer. Timesheets give you that too. In PWA it is called the Remaining Work field. I tell my customers to make sure to talk about the importance of that field with their resources when talking about the timesheet.
The other reason why information about the pure "How much work has been done so far" is NOT irrelevant is that the PM's job is not just about schedule. It is also about Cost. If all the PM gets is how much is left they will be able to do well on the schedule part but they will be blind to the cost trend of the project. Getting good information about how much work has already been done AND how much is estimated to be remaining is the only way for the PM to know how much they have already spent and how much they have left to spend. This would need to be compared to their budget in order to figure out if they will need more money or if they will need to cut features.
So I agree with Jack completely about the need for "how much longer" but I have to differ on the importance of a good timesheet in getting that info and on the overall benefits of a timesheet.
By the way if you have not been to Jack's Blog you should check it out. Very good stuff! Well except for this thing about timesheets. ;-)