The on-site interview was 3.5 hours in four different meetings with different people each. The second meeting was with a VP heading the optimization department. Everyone was not just polite but also nice. I have a positive experience from the whole interview process.
The questions ranged from (i) requests to describe previous operations research tasks I have worked on, to (ii) requests for explanations why I have worked in so many companies. The VP and a marketing guy asked me to tell them how would I talk to business, non-technical people.
Almost none of the group talked about themselves or their accomplishments and ambitions. The focus was on me.
In the last meeting with the hiring manager I figured that I am over-qualified for the job. The job itself might be intellectually challenging enough, but I did not see it as particularly demanding of my skill-set range. (Which considered together with the salary they are offering makes sense.)
They said they are going to pass on me because, although I have a great skill-set, I am not a good cultural fit and did not show myself professionally enough.
I assume this can be explained with my style of talking about mathematical and research subjects and observations feedback I give. Those are very suitable for start-ups that try to develop disruptive technologies (or think they do.) Apparently not so much for that group.
I am giving four stars out of five because, well, they could have been more accommodating than that they were. Like (i) offering drinks and snacks, and (ii) trying to sell the job to me.