I care about reviews and they do influence me on certain times on wether I buy a game or not.Be it because I dont have the time to research properly, or because you wotn know how the game will end up turning, reviews provide a definitive view on wether the game is for you or not.As long as you find a reviewer that suits your taste and writes well, you should regard his opinion on the highest regard.Not only because he is supposedely a professional and knows more about gaming than you(or should know more), but because he played the game.I dont have the time nor the money to buy and play shitty games, or even mediocre games.
And no, seeing playthroughts on youtube is not an option.It just spoils the game.
As for the scale, 0-10 is the best, and as many decimals and needed.The more precise it is, the better.
My (locked) thread about how difficulty should be a decision for the developers, not the gamers.
https://gamrconnect.vgchartz.com/thread.php?id=241866&page=1
