Aside from the 3 or 4 updates to biosdevname that changed the "immutable" names, I've just found another fail: I replaced my motherboard and since this one has native gigabit, I didn't re-install the separate NIC.
Naturally, my one and only ethernet interface is now called em1 instead of p6p1.
This really worked infinitely better before they solved this problem. All I had to do was remove the 70-persistent-net udev file and let it get automatically regenerated from scratch.