I've been building virtual worlds, games and game engines for 25 years, and the last year has been amazing. Last December was the start of a revolution, and in the ten months since, the models have just kept getting better.
These days I can sic Opus 5.5 on ten issues from my todo list, go to bed, and wake up to them fixed. It's always faster than I would have been, but speed isn't what impresses me. It holds every issue in mind at once and connects them in ways I never did.
It has real limits. It's great at connecting what's already there, but it doesn't invent anything. It's weak on visual detail, and consistency is a foreign word to it. You have to keep steering it. Do that well and it will blow you away.
Whenever I have tokens to spare, I point it at architecture reviews, code reviews and security reviews. It keeps the codebase tight.
Over the last year it has written 250k lines of code for me, it has generated all of the icons for the game, it has written retargeters to take Maximo animations and put them on my model. Damn.