Model nerfing is rampant from people using subsidized plans.
Stories are much fewer and further between for people using the API. Which makes sense, the subsidized plans are "You get what we give" whereas the API is "You get what you pay for".
Models being nerfed is widely speculated primarily by people whose first instinct after suboptimal results is blaming the tool.
It is not something that has affected productivity in any measurable way.
Concerns of AI labs illegally accessing your usage data to steal your business model are a similarly imagined problem.
Personally I make my business decisions based on real results, which are imo significantly better with the latest SOTA models.
The moment you find a money-making formula on top of someone else's black box model, there's nothing stopping them from taking it for themselves.