I use MariaDB on my Mac for most things that require MySQL. It's a drop in replacement for most things. Is there a special edge case with media wiki they had to solve or is it now just formally announced as being supported?
So, it's pretty much a drop-in replacement. But as with everything, time m ust be spent testing and so on before rolling it out to production. I believe a transition to MariaDB has been planned for a while now.
I remember I had problems with insert statements when previously with mysql inserts without default values worked but MariaDB was strict in this case and these inserts failed...