Long story short.... Updated the firmware like the instructions said (from Pioneer and utilizing the micro sd)...... Unit was stuck in a permanent reboot mode with no hard keys working. EVEN WHEN CAR WAS OFF AND KEY WAS OUT. After about an hour I had to undo battery terminal so I would put kill the battery over night and the next day.....

Now when car is turned on, NOTHING HAPPENS to the head unit. No lights, no power etc........

Any way to until brick, or did I just royally **** myself?

Looks like Pioneer sent out the INCORRECT update.  Best buy is currently sending it back to get fixed.  

I almost had that same issue. Unit hung after the update (before I installed teh BT firmaware). It was supposed to automaticlally restart and it did not. I had to disconnect power from the radio, replugged it in and after that worked fine. I was sweating bullets for a few minutes Saturday morning. I will check back periodically at Pioneers site hoping they revise their update, as there doese seem to be an installation issue with it.

Well I updated my pioneer AVIC-x940BT to the new 4.6 firmware and then my head unit rebooted randomly and the screen is black and the unit wont do anything now.  What should I do at this point???