I will second Plato's response. Several things seem inescapable when you consider this question dispassionately:
1) Good reviews matter a lot to manufacturers and they will do all they can to avoid bad ones, which do more harm than a good review, benefits.
2) It follows they will not give kit for a review, if they aren't sure of a glowing response.
3) Reviewers and editors know this perfectly well, so they won't publish a bad review.
4) If a magazine repeatedly reviews c--p in glowing terms, it will soon be obvious to everyone and they will be slammed here and in other forums and no one will buy the magazine.
5) It follows kit found to be rubbish will be politely returned, perhaps with a note as to why a review isn't being published.
These strictures apply to magazines online reviewers who don't take adverts, just as much, perhaps more. They have to borrow kit as well, for review and a manufacturer will be doubly suspicious when they know a big advertising spend, doesn't give them a hold over the magazine. This isn't my opinion, but what has been expressed to me, by a number of reviewers in sources which do and do not take adverts.
It follows, I believe, that magazine reviews can be relied on, with qualifications, as much as any other source of information. That is as a guide in making a short list of gear to be auditioned myself.
