Well I for one think he did an OK job.
As has been discussed on other threads Byron was given a poison challice, reduced budget and a complete sh1t fight on two fronts ( 1-staff/industry relations and 2-"the regulatory reform"process).
Here we are a few years later and relations are much better (not perfect) with the industry, I think the MOS ( manuals of standards ) are a good concept but very poorly written, there a many additions within these documents that are not supported in the legislation, personal opinions haved snuck into the requirements.
CASA appears to have formed into more of a corporation than a government department, but that was what the PM wanted.