Looks like there're two main approaches to AI-first development: (i) favor slow responses to produce an upfront high-quality result, (ii) favor quick responses to enable faster response-test-query iteration. And, based on comments read here, seems Codex isn't too fit for the later. Optimally a developer should be able switch between the two approaches depending on problem at hand.
the startup time is crazy, you can start writing as soon as you hit the command
(I don't use codex, just noticed that it's crazy fast)