Except when you need to scale.

Their query optimizer is incredible. Unfortunately that lets people get away with truly horrifying queries or views nested a dozen layers deep until it falls over.

Us it, though? I worked with it tangentially and found it deficient compared to Postgres. Why pay for a product that's worse than the best free product? In the old days there was a question of who to pay for support that was easier to answer for proprietary DBs, but with cloud services that answer is "you already pay your cloud provider".

I wish Microsoft paid more attention to T-SQL though. It’s an atrociously primitive language in some ways. There is no “record” or “struct” type of any kind, table-valued functions are not composable, an error in one line may throw an exception or just continue execution to the next line depending on whether TRY..CATCH exists at some higher level… to name just a few grievances of many I accumulated over the years.

It can work well performance-wise and security-wise, but programming it can be quite a pain, and I feel that’s unnecessarily so, considering what resources Microsoft has at their disposal.

I would use it if it supported backup/restore over unix pipes / ssh.