During the Office 2013 preview period a serious fault was identified by a number of users for Publisher 2013 that renders it completely unfit for purpose as a publishing tool.
As a brief summary, the problem identified is that of poor image quality, either on screen, in print or when exported to a PDF for embedded objects/documents in a 2013 Publisher document. This is most easily observed with Excel objects, please refer to this post within the Office 2013 Preview section of the forums which include images of the issue that are still relevant as of today (20th Feb 2013): http://social.technet.microsoft.com/Forums/en-US/officeitpropreview/thread/cdffa6e4-1bc4-4c8d-a883-70c2d5e2a885/?prof=required
It is also worth noting that a document created in an earlier version of Publisher, while appearing as expected within the earlier version of Publisher, on screen, print or when exported via e.g. Publisher 2010, will also have the associated poor image quality when opened within Publisher 2013. Conversely if a document is created within Publisher 2013 where it experienced the resultant poor quality, it can be saved and opened within e.g. Publisher 2007/2010 where the image quality will be rendered normal by the older software.
From my own personal point of view I use Publisher on a weekly basis in order to produce an in house live results book that is tied to a few hundred active spreadsheets and databases so that the data within the book is automatically updated when the Publisher document is opened. With Publisher 2013 this is impossible due to the very poor image quality associated with all of the embedded Excel spreadsheets. I would like to know if this is an issue on the radar for Microsoft to issue a fix and if there is an ETA for said fix. Until it is addressed, Publisher 2013 is impossible for our organisation to use, which is a real shame given how good the likes of Word and Excel 2013 are.