StingingVelvet: User review systems will always be flawed and never be reliable. They're cute distractions. If you want to know about a game on GOG I suggest looking up unedited gameplay footage on youtube.
If I come up a new game e.g. in GoG I am not familiar with, I usually go to check the user reviews in MobyGames. I usually find them somewhat reliable.
The problem with user reviews (compared to magazine reviews) is that sometimes mainly the people who feel very strongly (positively or negatively) about a game review it. That can give either a skewed or split view on the game, as if people only either love or hate the game. But then, strong reviews normally have more information on what was either right or wrong in the game, instead of mild "It was ok, I guess..." reviews.
On the other hand, the users are not pressured to make favourable reviews just so that their magazine can get extra perks (e.g. "exclusive previews") and ad money from the publisher in question, and they also seem to pay more attention to how e.g. the DRM affects the end-user, ie. analyze the final game, and not some review version that may or may not have same drawbacks as the final product.
The user reviews in GoG I don't trust as much because as said, some seem to praise any game just because it is in GoG (in order to support GoG), and review games they haven't played recently (or at all).