Any opinions on the value of this test (perhaps also from the "Shrink of the Org" )?
Sorry, can't say much on it. It got mentioned in my psychdiagnostics course. But I don't know much of it. It's based on Jung's typology though, that doesn't bold too well. The best personality test is the MPI-R, but I guess it's not very suitable for buisness needs. I'm rather sceptical of all personality test though.

I work in a psych ward where this is still used. I took it myself as part of training and it said I was slightly paranoid. I'm not taking that too seriously since some of the questions were like, "Do you take news at face value?" or something like that (it's been awhile).
That shouldn't worry you too much, the MMPI is mainly based on psychopathological probes. It tells you in what direction you're mad if you're mad.