Just a note for the record here, in case someone stumbles upon this who needs it. I just did the EFI update and the 10.8.2 update on an rMBP (2.6/16/512) that had FileVault2 enabled already. I also had verbose startup enabled. I was not watching it too carefully, but at some point the screen was black with no activity. It turns out that it was sitting at the FileVault unlock/login screen (pre-boot), which was not visible. I just put in my password blindly and hit return, and it booted up normally. Thank goodness my (main, production) computer wasn't hosed.