I had a permanant retainer on the bottom originally; I didn't think they did them for top teeth. It was very simple: literally just a piece of wire attached behind the teeth (invisible to others). After a while, mine came loose and poked me painfully (and, of course, it happened at the worst possible time), and I asked for a removable type for the replacement.Most will not even tell you about perm. retainers. I did initially inquire but was discouraged because of the difficulty to clean around them.
Negatives:
A permanant retainer makes flossing impossible; thus it makes cleaning more difficult.
It's there all the time; you feel it with your teeth the same way you feel the braces with your lips. Eating is still somewhat hampered, though much, much less than the actual braces.
They CAN break or come lose -- mine did.
They interfere with dental x-rays (like many people, I had my wisdom teeth pulled right after my braces were removed, and I remember the dentist commenting on this).
You can't enter the military wearing a permanant retainer (a high school friend had to have his removed before accepting an ROTC scholarship).
Positives:
You can't take it off or lose it, which is safer for a teen who might not be so responsible.