I am a machinist. I spent at least 40 hours over the last two months machining styrene. In this case, exclusively with a mill. I assure you, professionally, that cutter speed and feed rate were not a problem. I clamped everything appropriately, and there were no "blowouts". Only thing wrong was the white fuzz all over the place. The static-y white fuzz.
You are right about setup frequently taking longer than the work. I have made many fixtures. It may well take longer using a mill than a table saw; but much less can go wrong.
I bought 2 cars, cut long and sanded. More than once. I'd prefer not to do it anymore. I do not enjoy it.