Of course an MMO dominating sales charts is nothing new. World of Warcraft has done so on and off since its launch four years ago, and Age of Conan debuted at #1 in many regions, even defeating the critically acclaimed BioWare tactical RPG Mass Effect which launched in the same month. It's also worth noting that the Warhammer IP is very popular in Europe, perhaps more so than in North America.
This news jives well with the report that half a million users have registered for the game. On the other hand, similar numbers were thrown out around AoC shortly after its launch. It's doing okay, but it didn't turn out to be a landscape-altering success that some folks projected, and that some are expecting from WAR as well