GPT 5.5 on Medium is all I use lately, I don't understand why anyone would pay drastically more for slightly more, when Opus has been good enough for a year now to do most things.
That’s a little telling of the state of ai atm though isn’t it? It’s all pretty similar. The latest Opus/GPT/Gemini/Deepseek/Kimi on medium does indeed do the job
To your point, though, I don't know if I've noticed that big of an impact going from 5.5 to newer GPT models. If I had to switch back, I'm not sure how much I'd miss the newer ones. People talk about e.g. Opus 4.6 similarly, I've noticed.
The bigger change in OpenAI-land IMO is the models got cheaper, generally.
Though, it has been a while since I've used 5.5.
But for webdev, deep research, code review, and a few other tasks I find the current 6.1 sol better.
But I use both. And I use codex more.