I have taken it a couple of times and seen others take it. Seems pretty accurate.

This podcast does a pretty good analysis of the historical origins and scientific evidence for M-B:
[skeptoid.com]
In a nutshell, it's better than astrology, but not by much. Everytime I take it I get different results on 3 of the 4 domains.

I like Gregoric better as a learning style indicator.

ENTP. It's a good way to put people into generalized buckets but does not account for personality quirks of an individual. Once you get into the NT types people have their own distinctive weirdness that sets them apart from the buckets. Also people tend to vacillate between classifications and flip letters depending on mood. I can be ENTJ or INTP sometimes (I have tested as both) as I work wirth those kind of people and have many as friends. Kind of a chameleon effect when we try to fit in or relate to others. So it's a good starting point for putting yourself into context but not a hard bound indicator of personality.

In my opinion it doesn't mean any more than any other 'personality quiz' you find on the internet. I don't even remember what my result was other than that it started with 'E'.