5.2.1 update just ruined my whole install... give me a break!
Updated Atheros (rebooted fine), but then updated FakeSMC.kext(backed up my old FakeSMC.kext) and the ALC8XX kexts for my GA-z77-DS3H (3770k CPU) and it stays on the gray boot screen. So then I replaced the FakeSMC with my old, reboot, but still not luck. Then removed the ALC8xx stuff and still nothing. Bullpucky update.....if you ask me. Getting real tired of MB's
EDIT: NEVER MIND!!! I think the Audio kext was keeping me from booting. Got it back up and running