In 2.79, running a preview render would let me see how long it would take for me to complete a certain number of samples. This was useful for me as I would often times set my preview samples to a number that is approximately equal to how long I'll be away from the computer for, or for me to gauge how long a particular scene might render on a certain sample setting.
Now in 2.8, I only see this:
How do I get back that indicator?