Fable works very well for me on a moderately large codebase. I have had to correct it a few times or point it on the right track, but given how much faster it is at programming than I am that's a very minor issue (and most of these errors are because I underspecified what I wanted in the prompt, I can only think of two cases where it was genuinely wrong... that's a lot better than me in my professional career). Code quality is equal to what I would come up with (and better in areas I'm not familiar with) and the overall software engineering bar is higher because it doesn't get bored when I tell it to do refactors or write integration/regression tests that I would otherwise put off. Also makes it easy to audit code for things like missing audit logging or error notifications that a human would get bored doing.

The product is a fairly standard Ruby on Rails webapp with postgres as the DB. Application complexity is probably a bit higher than average for a webapp. So it's nothing that pushes the boundaries of software engineering, but it is a real product. Token budget has not been an issue for me. I pay for the Max plan ($200/month) and it is well worth it.