My Simplify3D time estimates are consistently in error by a factor of 2. I just take the estimated time and double it to get the actual time it will take. The thing that bugs people so much about this error is that the free slicers do a much better job at estimating the time. At least that's been my experience. Slic3r and Cura both do much better in this regard.
That and I'm weary of seeing time estimates in minutes (on the machine control panel) when the time value is greater than 60. This should be configurable by the user. How many hours is 446 minutes? Have to grab my calculator every time. It's much more meaningful to display "7 hours, 26 minutes." How easy is this to implement? I could do it in one line of code.
-Mark