Very good post!
As a manager I'm used to do this interviews all the time. I find them very pointless but it's a company standard.
I do support more the "trial shift" part, as it's better to see if a person will be good at the job or not.
At the normal 1 to 1 interviews the only thing I can see is who has been in loads of interviews before, as they come most of the time with all answers "prepared". Times to times someone really surprises me with creativity in some of the questions, but creativity doesn't mean someone is able to do certain jobs.
Upvoted ;)
RE: Why I Hate Job Interviews