A deterministic LLM isn't going to behave appreciably differently from a non deterministic one if your input or context varies by even a tiny bit (pun intended) each time.
i'm hoping that it becomes more useful as models improve and become more reliable at producing working code (though determinism would be great for improving prompts).
Really? If you include the seed as one of the parameters most produce pixel identical output.
E.g. "Generate deterministic images" https://cloud.google.com/vertex-ai/generative-ai/docs/image/...