It would be nice having an output which prints out the calculated difference between the current and the previous line.

00:00:00.000 Started...
00:00:01.256 Doing something
00:00:12.245 An other step.
00:00:00.657 More things..
...

With this output i can directly see that the 3. line take 12.245 seconds to execute...

This would make analyzing performance issue very simple.