biosdevname strikes again :-).
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.