How do you know they are impartial or even real customers?
In reality, the average customer will only make comments on a service that is poor or not what they expected, 'glowing' reports are mostly made by people with something to gain, that said, there are two "well known" websites that you truly can be sure that the 'feedback' is genuine, which are Amazon and eBay, because to leave 'reviews' the people involved have to either purchased the item from the site or sold it on the site. Just look around at any "webmaster" discussion forum, and you will find many complaints about various hosting providers and very few threads that start off saying how great that [a hosting provider] is.
"Hosting review" websites have no such controls, anyone can sign up for an account, they have no need to prove they are actually 'customers' of the "hosting company", or users of the service they are 'reviewing' and they can post wonderful 'reviews' of something they have never used. By all means use the information, just do not trust it implicitly. The 'reviews' that tell you most about a company are the bad ones, and it is how they have handled the complaint that shows how good their customer support and services are.