I’ve upgraded a couple sites to ACF Pro 5, and have also been using it on some new sites. So far overall, great!
One problem that keeps happening:
1) Existing sites that I’ve upgraded with existing ACF field groups end up with duplicated fields. Everything is the same in the field name and the underscore version.
*And if this helps at all, I upgraded a site to ACF Pro 5, then exported all ACF groups in a downloaded file, and imported that file into a new WP fresh install with ACF Pro 5 (the site never had ACF 4). The duplicated fields were still present.
So…I’ve just been deleted the second copy, but I’m afraid maybe there’s database mess left over? I don’t know enough to check. If it’s just a matter of removing the extras, and the database is clean, then no big deal.