My two cents on reviews:

If you read a wide variety of reviews from a number of different sites about the same game, it tends to give you a pretty good picture of what the game is going to be like. Say, take a site like Metacritic -- ignore the top 3 reviews and the bottom 3 reviews and read two or three that in the middle of the pack, and you'll probably get a general sense of what the game is like. That is, completely ignore the score giveen and read the review. Number based scoring systems are open to wide interpretation. What I might give a 6/10 might be someone else's idea of a 7/10, because they think anything rated 6 or lower is essentially a waste of time.

Then you kind of have to factor in reviewer bias towards that specific genre or series. I tend not to trust any reviews at all about the huge popular games (Grand Theft Auto, Elder Scrolls, Marios, Zeldas, Call of Duty, etc) because most people are so deeply in love with those series that it is sometimes hard to actually see the flaws in the game. I know I'm like that with Zelda games -- even if the game isn't perfect or doesn't make sense, I'll still rate a Zelda game 9.5/10 almost every time.

As for purchasing reviews... yeah, it happens, and likely always will. I think the bigger concern is reviewers receiving special promotional packages that also enhance their view of the game. Receiving a reviewers copy with special perks like figurines or general merchandise creates a goodwill towards the game that will most likely shine through into the review where they want to say something good about it because they were treated well when they started playing it.

There's also the problem of most reviewers on the big sites (IGN, Machinima, EGM, Eurogamer, and probably hundreds more that I can't think of at the moment) don't actually pay for all of their games. If they don't have the $60 investment into a title that the rest of us make on Day 1, then they will likely view the game in a more positive light, or downplay the flaws because they didn't seem like a big deal to them at $0, but it would be a huge deal to us for $60, or even $30 if we wait a year for the price to drop. I'm not sure how well most reviewers can separate "playing for work" from "playing for pleasure," but I have sensed that because some reviewers are playing a game "for work," they aren't coming at it from the same mindset as someone who has a small amount of time they can commit to any game at a time, and therefore things that might bother the average gamer doesn't bother the reviewer, because they're sitting there playing for 6-8 hours in "work mode."

I don't know how much of this is actually true, but it's a sense that I've gotten while reading.