From my experience with WoW the performance is one of its biggest strengths and no doubt a major reason behind its success, its a very well optimized game. Bear in mind that when comparing WoW's performance you don't compare it to normal games, you compare it to other mmo's, ofcourse an offline game is going to run and look a lot better, but there is a pretty huge difference in how much is going on in the game. Normally i play at 1680x1050 with 8xAA, everything maxed out, this is on a E8400, 8800GTS(512), 4Gb RAM and Vista 64-bit. It runs smooth even in cities. Tried running a second client on another monitor at the same time, at 1280x1024, still smooth. If only more developers could follow Blizzards example when it comes to optimization, pc gaming would be in a lot better state.