As someone who owns a web hosting business, and recently migrated all of their servers from MySQL to MariaDB. It was the easiest transition we've ever performed. On our cPanel boxes it was done in just a couple of clicks.
MariaDB really is a drop in replacement for MySQL. They have done an awesome job ensuring its a dead simple upgrade.
We are currently looking into upgrading our DNS network. We are toying with MariaDB Galera, and PowerDNS. Our initial testing has been very positive.