In my experience and perception of the world:
I think there are correlations that are true. But to "define" someone, I think is a little much.
I think theres also one of those fortune cookie dillemmas here, for example - i have relatively sloppy writing. Sometimes I don't dot my i's, I write my signature a different way everytime, and i write to fast. From this you can draw:
a) I'm a really rushed person
b) I'm free spirited
c) I don't care
d) I am mentally or physically incapable of writing my name the same way
e) My values do not put writing very highly.
Two of these are true, most of the above are not. It's really easy to try and draw accurate conclusions when there are so many possibilities.
Not to say some are not good correlations.