The NDSA has released The Benefits and Risks of the PDF/A-3 File Format for Archival Institutions.
Here's an excerpt from the announcement:
The report takes a measured look at the costs and benefits of the widespread use of the PDF/A-3 format, especially as it effects content arriving in collecting institutions. It provides background on the technical development of the specification, identifies specific scenarios under which the format might be used and suggests policy prescriptions for collecting institutions to consider.
For example, the report suggests that for memory institutions, the acceptance of embedded files in PDF/A documents would depend on very specific protocols between depositors and archival repositories that clarify acceptable embedded formats and define workflows that guarantee that the relationship between the PDF document and any embedded files is fully understood by the archival institution.
Additionally, the report notes that the complexity of the PDF format and the wide variance in PDF rendering implementations and creating applications suggests that PDF/A-3 may be appropriate for use in controlled workflows, but may not be an appropriate choice as a general-purpose bundling format.