I'm not really sure if this should go under Mavericks or Yosemite because I'm getting Yosemite-like behavior after reinstalling Mavericks. I heard someone on this forum mention that Yosemite did a firmware update so they couldn't downgrade. Well, I wiped my drive and reinstalled Mavericks and I've noticed one thing. In Yosemite, my rMBP would boot to a black screen and a white Apple logo. In Mavericks it used to boot directly to a bright screen with a gray Apple logo. Since reinstalling Mavericks when I cold boot my system It boots to a black screen (I can tell the screen came on) for a few seconds before it resumes Mavericks-like behavior. Has anyone else noticed this after running Yosemite on their system at one time or another?