The EFR (Enterprise Feature Router) is single-threaded. For those features running through the EFR, they can only run, one at a time. So if you have a service that is doing PDF file conversion from MS Office 2010 Word and PowerPoint, it can only create one PDF at a time, whereas Enterprise edition can multi-thread them and do several at once.
You still get access to use all of these great new features, but if you have two requests trying to use one of these Enterprise features, the second one will queue and wait for the first to complete.
Regards,
Anit Kumar