It appears that the TFS 2012 burndown works a bit differently than I expect.
Suppose my current iteration is at 100 hours remaining out of 200 total original estimate, and my three team members each create a task today, estimate each at 6 hours, and complete these tasks. Thus, we discovered and completed 18 hours of work that we didn't realize were there. I would expect the entire burndown to "shift up", have it recalculate based on 218 hours total, and we would now be at 100. Thus we would show a good burn for today: we burned down 18 hours, going from 118 to 100, remaining. The goal burndown line would get a bit steeper, and we would reevaluate if it is realistic given the newly discovered work.
However, it seems that TFS's burndown chart ignores the "original estimate" in some (all?) cases and would show no progress today; those 18 hours are not reflected anywhere in the burndown.
This doesn't quite make sense to me--the upshot is, if I create a task today and finish it today, no hours are burned; but, if I create a task today, work on it today, and finish it tomorrow, then some but not all of its hours burn. Really?
How best to deal with this situation? Do we need to change the way we think of this?