There are many possible issues with regards to the paper version. Since the eBook is available, I would guess it is a logistics problem or production issue of some kind. Either getting the needed material to the printer, printing equipment problem, scheduling, binding, or shipping problem.
I now buy both the eBook and printed copy. With the eBook option I get both the PDF for my computer, and the ePub for my Nook Color eReader.
I also buy through Oreilly Media and I have access to any errata or revisions.