I was surprised to experience this with the voice upgrade. When they enabled advanced voice mode for everyone a month or so ago, the new voices were clearly more slow and annoyed seeming. I miss my PhD assistant, I don’t use the voice nearly as much anymore.
The surprise deprecation of GPT-4o for ChatGPT consumers - https://news.ycombinator.com/item?id=44839842 - Aug 2025 (140 comments)