Okay, might be a feature for most people because you can continue the work on that or any other document while the PDF export is in progress. But most of time I want to open the PDF in Acrobat or pass the PDF to another application after it's created. Now you have a zero kB PDF file until InDesign is finished with the export.
The following hint works in CS5, CS5.5, and CS6 as well:
Create a new blank text file with the file name DisableAsyncExports.txt and place that file in the InDesign application package itself (right-click on the application icon and select Show package content). Then go to the sub-directory Contents/MacOS and place the new file there.
After a restart of InDesign the progress-bars are back again, and you can tell immediately when the PDF is created.
[crarko adds: I suspect this is one of those things that will be undone by a software update. I would strongly suggest making a backup copy of the InDesign application file before making any changes, just in case. Out of curiosity, can someone using the cloud-based version of InDesign let us know if there is a progress bar or not?]