One thing to consider is when reviewing HEA, there are rarely objectively "bad" products to review. It's a competition for preferences above a certain quality threshold. So regardless of the incentives, it's easy to say good things about good things. Individual reviewer credibility is in the eye of the viewer/reader.
The ones who are more suspect are the "high end for less" folks. They may have an incentive to hype lesser products for financial gain. Or they might have good tips. Buyer beware.