Not OP but I had great success letting it repeat stuff we already have, for example we have a certain pattern on how we place translations. So I just hardcode everything and in the end tell it, using a pre-written task I can just call up, to take all the hardcoded labels and place it im our system in the same way it has already been done. It then reads the code of a few existing components and replicates that. Or I let it extract some code into smaller components. Or move some component around, it can do that batter than the IDEs integrated move action. Completely novel stuff is possible but I am uncertain if I am actually not slower using it to achieve that. I mostly do it step by step, really small steps that is.

I have to measure my performance at some point, it is certainly possible that I am actually slower than before. But overall I never liked typing out the solution that is in my head, so using it as writer is nice.

Sonnet 4.5 is what I use. Some colleagues like GTP-5 but it struggles real hard to do the most basic things right in my experience. Claude is just miles ahead.