Today the MySQL blogs are talking about a change that Oracle is thinking of making in MySQL 5.7. The change: to enable ONLY_FULL_GROUP_BY by default.
Apparently this is a very big deal, even though it is just a default setting which can simply be disabled (like most things in MySQL that provide reliability).
I guess I'm pleasantly surprised that so many MySQL actually know about this feature...
See also: http://www.tocker.ca/2014/01/24/proposal-to-enable-sql-mode-only-full-group-by-by-default.html