This is 100% consistent with my experience. Its been clear that they are nerfing it on the back-end to deal with copyrighted material, illegal shit, etc (which I also think is bullshit but I accept is debatable).
Beyond that however, I think they are also down scoping the queries from 4 to 3.5 or other variants of '4'. I think this is a cost savings measure. Its absolutely clear however, that 4 is not what 4 was. The biggest issue I have with this is the issue of "What am I buying with a call to a given OpenAI product?". What exactly am I buying if they are re-arranging the deck chairs under the hood?
I did some tests basically asking GPT4 to do some extremely complicated coding and analytics tasks. Early days it performed excellently. These days its a struggle to get it to do basic asks. The issue is that not that I cant get it to the solution, the issue is that it costs me more time and calls to do so.
I think we're all still holding our breath for the 'upgrade', but I don't think its going to come from OpenAI. I need a product that I'll get consistent performance from that isn't going to change on me.