Regarding the limitations with DATA SYNC across MySQL versions I rewrote the FAQ to take the change with SQLyog version 5.1 into account.
http://webyog.com/faq/11_68_en.html
The important thing is that most limitations with SJA DATA SYNC across MySQL versions have gone away as the check for NULL-constraints was removed in one of the late 5.1 betas. This – I think – should have had a little more attention than it had. That is why I write this here!
😀