Very helpful. Appreciate your effort in posting all this knowledge and especially the links. I recently decided to upgrade my 2011 MBP HDD to a Sandisk Ultra 2 SSD. The cloning was done using SuperDuper and everything went very smoothly. Except for when I put the SSD inside the MBP the boot sequence is stuck on the grey screen with the Apple Logo and the rotating gear. Very frustrating. The laptop won't boot even if I plug the SSD through USB and pressed "Option" at startup. Clearly there's something not right during the "launchd" phase. Your articles might help so thank you again.
If you have any other words of wisdom for my situation kindly let me know as I'd appreciate any help I can get for this situation.