My experiences (one long-established regional and one major - several mergers) were almost uniformly positive. The attitude was that "you're one of us and we're gonna get you through". Study, follow procedures, do as your told and you'll usually come out fine. The programs are usually well-established and time-tested, and there's a pilot group (and other experienced trainees) to answer questions.

I hear horror stories, though, and I'll bet you get a few of them on this thread.