Metacritic scores aren't completely worthless but they're pretty darn close. Reviews, however, are valuable tools in which to learn more about a game. I like to read several before I buy anything. The scores themselves, though, are only good as a very rough guide.
I've said it before, but my own +/- on a metacritic scores is around 10 points, at the least. That means if a game has a meta of 80, I simply think of it as being in the 70-to-90 range, or perhaps even beyond that.
The one thing that always puzzles the hell out of me is how people lose their minds if someone gives a game they like a lower score. Really, who gives a rat's ass? It's another person's opinion about a game, we read wildly varying opinions on the forums all the time without slipping into rage mode.
And why do people get puffed up and indignant when a game they like with an 85 average gets a 60 but not when it gets a 100? If the outrage is over the size of the deviation, surely one is just as bad a review as the other?