I know of several multi-million dollar business ventures happily using .biz - but as with any domain, all the seo factors come into play, including keyword competitiveness. I would say that a nice, neat .biz is better than a 60-character-multi-hyphen .com
If you say to someone you run a company called "red ink" the first thing they will try is redink.com.
90% of the time when I have guessed a URL to a website for a company, band, or anything like that - it has been correct.