Does anyone use MariaDB in production? If so, why over the competitors?
Also, we like the percona performance patchset that made it into MariaDB and isn't in MySQL proper along with the pt-* toolset from percona.
Many Percona patches did make it into MySQL 5.7 and MySQL 8.0.
I don't quite see the unique advantages of MariaDB compared to current MySQL, PostgreSQL, SQL Server, CockroachDB, MemSQL, etc.
In my case we switched to MariaDB because it fixed a number of glaring query optimizer failings much sooner than MySQL. And we've stuck with MariaDB because it has been much smoother and confidence-inspiring than MySQL when we used that.
We also use the TokuDB storage engine extensively, which is well supported by MariaDB. Whereas MySQL 8 is going in a very opinionated direction that I personally don't agree with.