Personally I like it, and it catches bugs right away, especially when there are multiple possible ids, e.g. func AddMessage(u UserId, m MessageId) If it's

Personally I like it, and it catches bugs right away, especially when there are multiple possible ids, e.g. func AddMessage(u UserId, m MessageId) If it's just func AddMessage(userId, messageId string) it's very easy to accidentally call as AddMessage(messageId, userId) and then best-case you are wasting time figuring out a test failure, and worst case trying to figure out the bug IRL. V.S. an instant compile error. I have seen errors like this many times, both written by myself and others. I think it's great to use the type system to eliminate this class of error! (Especially in languages like Go that make it very low-friction to define the newtype.) Another benefit if you're working with any sort of static data system is it makes it very easy to validate the data -- e.g. just recursively scan for instances of FooId and make sure they are actually foo, instead of having to write custom logic or schema for everywhere a FooId might occur.