Between the original rules and the FAQ, the Dedication Bonus section seems a bit of a mess, so can I please confirm that the following interpretation is correct:
If a character completes a career (ie completes all 10 General Career Advances), he may spend an advance to check the Dedication Bonus box. The career’s special ability becomes a permanent ability, and the character learns a specialisation for each of the career’s key skills he trained during his time in that career.
If he does not complete the career, or does not spend the extra advance before moving to a new career, he does not receive the special ability as a permanent ability, and does not receive the key skill specialisations.