I'm now sometimes using GPT3.5 because it produces better results than GPT4. GPT4 was amazing when it first came out for me. Either it has deteriorated or I was lucky in the beginning and am now lucky with GPT3.5 from time to time.
I have the same experience. GPT4 seemed surprisingly better at first, but now I can't tell a big difference between the two. Admittedly I'm bantering back and forth about history, literature, and languages...