While the demo part is trully a problem because of the media ....mmm how can i say this without problems again, let's call it, "love for suitcases with money", where they will give a bump or bury a game depending on "the suitcase size", or even some of their nationalism and love for their games. We saw a Witcher 2 working well with amazing graphics and a skyrim with mediocre graphics all bugged literally unplayable in some points, but skyrim got 9.7 and the witcher 2 bellow 9 in release, this examples goes on and on until now with IGN saying a game was wrong in some point (famous joke) too much water on it.
In other hands. real gamers and most people notice this "media incoherences" when some game is good, and developers wouldn't care about that scores as much people scores and sales. But fear is reasonable.
Benchmark is something good, no reason to not get one.