I've been vocal in my criticism of how user ratings were changed since the Gamespot redesign. At first, all user ratings were lumped together across platforms for any given game. Gamespot fixed this, and now you can find each version of a game with its own user ratings and Average User Score.
(Whether those user ratings and Average User Scores are more or less accurate than prior to the redesign is open to debate. I've again been vocal in saying that the number of user ratings for each version made sense before the redesign, and now they don't - often, 90% of the user ratings get allocated to one version now - but edgework from Gamespot has already told me his position, and it is what it is - I know he worked hard on this issue, and even if I disagree with his conclusions, I don't need to repeat that debate here).
Now, I'm finding that for many games that had expansions, the exact same problem exists - the user ratings are lumped in across the various expansions. If you look up the Average User Rating for Dragon Age: Origins on PC, for example, you're not getting just the user ratings for that game. All the user ratings for that game's various expansions are included in the average. This can have a profound effect on the overall user score when a game's expansions don't live up to the quality of the original. It also messes with the data for the original game - often, I'm finding that the release dates are based on the expansions, or that you can't even see reviews for the original or an expansion.
So far, I've found this problem in Borderlands, Dragon Age: Origins, Galactic Civilizations II, Lord of the Rings, Battle for Middle Earth II, Lord of the Rings Online: Shadows of Angmar, Mass Effect 2, Sims 3, Space Rangers 2, Spellforce 2, and Warhammer 40,000: Dawn of War, but I'm probably just scratching the surface. I started reporting this on the game-specific bug reporting topic in this forum, but this seems like a systemic problem that merits its own topic.