The marketing copy and the current livestream appear tautological: "it's better because it's better." Not much explanation yet why GPT-5 warrants a major version bump. As usual, the model (and potentially OpenAI as a whole) will depend on output vibe checks.
I think the biggest tell for me was having the leader of Cursor up vouching for the model, who has been a big proponent of Claude in Cursor for the last year. Doesn't seem like a light statement.