They aren't XMPP specific, but OTR as implemented in e.g. Pidgin goes above and beyond in making them bad – archiving is either plain text or disabled, keys can

They aren't XMPP specific, but OTR as implemented in e.g. Pidgin goes above and beyond in making them bad – archiving is either plain text or disabled, keys cannot be changed at all (so not even manually syncing them is possible), and session handover doesn't work (there's a session management implemented, but it doesn't do anything except silently eating messages).