I am using the Responses API. Prompts with c. 4k tokens have gone from a c. 5 seconds to 30+. I had to go through all my tests lengthening timeouts to even see what it is producing. The ones I looked at did look nice, but niceness at that cost is not worthwhile. I was unable to run a full eval run due to the slow response times. Gave up, went back to 4.1 for now.
Maybe you do need to tune the extra parameters, but at the moment I would not be able to run enough evaluation to assess the quality of the ‘less thinking’ version.