We certainly are. We're operating an analytical service operated on PostgreSQL - tens of TBs of data, hundreds of machines, tens of thousands of clients. Initially it was running on MySQL, but because of various reasons we migrated to PostgreSQL ~3y ago and never regretted that.
The reasons were both technical (better performance with this kind of workload, great reliability, excellent code quality, ...) and political (we have contributed numerous patches to PostgreSQL - not sure if you ever tried to do that with MySQL).
If you think there's a simple MySQL -> PostgreSQL migration tool (or a migration between arbitrary databases), you're foolish. Databases are not that interchangeable - all databases have some issues with specific workaround, and the 'good bits' are database-specific too. And those things are anchored in the application code, so if you think there's a simple migration tool, you'll be disappointed.
The reasons were both technical (better performance with this kind of workload, great reliability, excellent code quality, ...) and political (we have contributed numerous patches to PostgreSQL - not sure if you ever tried to do that with MySQL).
If you think there's a simple MySQL -> PostgreSQL migration tool (or a migration between arbitrary databases), you're foolish. Databases are not that interchangeable - all databases have some issues with specific workaround, and the 'good bits' are database-specific too. And those things are anchored in the application code, so if you think there's a simple migration tool, you'll be disappointed.