Unfortunately, they don't influence the careers of professors. It would improve the teaching standards if the teachers who got unanimous negative feedback were reprimanded. Right now, teaching is sort of volunteer work. It has no reward other than teaching. So, if you really like teaching, you put the effort. Others who don't like it, do just enough to get by. It is really unfortunate that teaching is not given even 50% of the importance given to research in most universities.
They are a useful tool for a teacher though. I usually take the feedback seriously, so that I can improve myself.