I know of a few guys who went to QF, couldn't stand the culture there so came back. They had to restart their seniority from new DoJ. If you try to rejoin within a short period of time(2years I think) they can take you back without all the interview hoopla. After that you have to do the whole interview process all over again.
If you didn't burn any bridges they will consider you. But obviously they will be focusing on why you left and how it is that you won't leave again.
Good luck.