I know Angie's List, Yelp and TripAdvisor focus heavily on reviews. For a business site that includes professionals, are reviews a good feature?
Reviews are a powerful capability that gives credibility for transparency. You also have to be prepared for those open conversations - as you know from referencing those three sites. This means committing to authenticity (as cooked reviews are a major mistake some have attempted) and navigating the appropriate moderation of reviews.
It really is driven by what your B2B goals are on your business site. Some sites have handled building credibility through questions and answers (i.e. Quora, LinkedIn, et al). There you can allow users to rate answers - and also allow for flagging of those that don't pass the genuine test.
I call it the Amazon effect (others use eBay) as they were among the first to offer reviews on a massive scale. It is powerful and influences decision making, purchasing and attitude toward products, services or even the site itself.
Having designed policies for social communications, customer service communications and more in B2B environments - I've seen reviews work well and not so well. It can be done - but requires judicious planning for rules of moderation and engagement, and for how readers of reviews can reward or flag them.
I'd be glad to hold a follow up on this and talk through those elements.