field_get_items('user', $user, 'field_name') empty?
I was experiencing the same issue. field_get_items was always empty when trying to get a field attached to a user. The problem was that the $user object you get when you do a 

global $user

isn't the full entity. So when you pass it into the field_get_items function, it doesn't match anything.

Do a full user_load on the $user->uid and THEN pass the resulting object to field_get_items, and everything should work.