[closeparen]

Shipping to large numbers of users in production, getting the metrics back, investigating alerts / bug reports, finding edge cases in real data, and solving them.

Now I have a handle on the sorts of things that can go wrong / are going wrong in the real world, some earned confidence in my ability to fix them, and general upward trend in my ability to anticipate and prevent them during development. On the other hand I no longer have any trust at all in code that has not been put through real-world usage or where I don't have access to feedback from real-world usage. Reality is much better at generating interesting test cases then we are.