The various conditions are rare, but not very rare.
Very rare would be something like Town’s Syndrome.
http://www.isna.org/faq/frequency
As noted before, this isn’t the same thing as a dude deciding he’s a chick.
Down’s. Autocorrect is messed up.
An interesting list, but not all of them should be difficult to assign sex. XX with congenital adrenal hyperplasia, early or late, is a girl who needs hormonal therapy and who may or may not need surgery to correct pre-treatment viralization. XY with hypospadius is a dude with plumbing rather than gender, problems. The one XXY patient was a clearly a guy the XO patients I’ve seen are clearly girls. Androgen insensitivity is probably the least rare hard call on that list. Though XY, the Y is blocked from working and we don’t know to turn it on. They look like normal gIrls and may not learn otherwise until puberty.