Personally, I appreciate reviews that are honestly critical of products. If I want a review that's all butterflies and rainbows then I'll watch the promo videos from the maker of the product. I then reserve my opinion until I actually get to experience the product first hand, pay attention to the issues noted, then make my own decision.

In my previous job, I was constantly being presented products/solutions by vendors for my company to represent and was always told/shown how great they were with hardly any critical evaluation of the products, especially within the context of competing products. I pretty much formulated a method of letting the manufacturers present to me but limiting their time to about 30 minutes. I would always follow-up by saying thank you and how I appreciated them highlighting the positive things their products should do anyway, and would then proceed with several critical questions related to things their product did not do, did inefficiently, or wasn't as good as other leading products in the space. The response were quite varied, and sometimes people really exposed themselves as not being very sharp. However, I always appreciated the ones that had good responses to my questions which showed me they actually knew their products, competition, and market space well.