.biz has the lowest profile (and publicly reported aftermarket sales) among the .US, .info, and .biz trifecta. That being said, .biz has 2 million + global registrations. And I see notable numbers of local businesses using .biz. Quality one and two word .biz domains are good investments for business-specific purposes: real estate, marketing, consumer products, etc.
.BIZ do not flip as easily in the domainer market as do .us and .info. So whether or not .biz will be a good investment depends on 1. how long you intend to hold, 2. the quality of the domain you're considering, 3. the robustness of the market described in the domain.
An indication of that last factor is to type the domain into google as in "Boston Homes", and then count how many Google advertisers are purchasing ads for that particular search phrase. If it's 2 or 3 ads, then that may be a weak market. If you have many ads, then the market interest is apparently pretty hot, and your resale and/or monetization options are likely better.