A couple of years ago, I was at Google's office, and I talked with someone who works on search about .biz extension. They said domain extension doesn't matter. At that time, they said backlinks is one of the most vital signals apart from some PR. That was like eight years ago. So I never changed the domain name despite owning the .com version too. It will break too many backlinks.
Sure, google might be fine with a .biz. As a human consuming googles responses, my eyes typically glaze over seeing .biz and jump to the next search result. It's not that there is anything particularly wrong with .biz, but this is the first legitimately useful site (to me, probably plenty for others) i've heard of using .biz.