There is a topic in this community that asked a similar question 2+ years ago. At the time, Bernie Thompson noted that a mix of USB 2.0 and 3.0 on the same hub will cause all devices to communicate at USB 2.0 speeds, using OSX 10.8.2.
http://support.plugable.com/plugable/…
I am wondering if this has been tested lately, and if there has been any change in this area, i.e., if Mac users can have USB 2.0 and 3.0 devices on the same hub, working at (or close to) their max speeds.