You wouldn't have to do that. You'd only need check a few games and see how close IGN's was to the final average. Perusing GameRankings, quite often IGN are within +/- 2% of the average. And then sometimes they're out by 10%. (Or you just find and click the statistics link, if you happen to know there is one )So you've broken down every single site's reviews and compared them to the gamerankings average.
Though IMO it's silly to second guess the scores when you only have to wait a while. Why try to predict the average score from one or two reviews? Why not wait for GameRankings and Metacritic to turn in the averages?
As it is, Metacritic has HS at 83% and GameRankings has it at 85%. Early days yet, but it's not the 'HS is no good' score that some (notably a friend of mine!) had been jumping to conclusions with. And scores aren't much use. While looking at GR scores to see how IGN fairs in picking the average score, you come across some interesting figures. Driver, the original PS game score 97% with IGN, the average is 88%, and Gamespot gave it 77%. Depending who you follow, it's a truly excellent game, a good game, or an okay game. As it was, it gave us a huge amount of fun. Lots of mates gathered around the TV taking turns to do missions, and helping each other avoid the fuzz. Not many games are good a spectator experience. I'd give it 10/10 for enjoyment, despite weird bugs, graphical glitches, and on occasions terminal difficulty.