When the expansion came out, things got a little slower for my PC. As each successive patch came out, things got worse. It was getting to the point where the game was crashing regularly, particularly if I was catching a taxi anywhere. I thought it was my video card, until a guildie asked me to check out my CPU usage (listed in the Task Manager) when I was just idling in Shattrath... it was nearly 100%. So definitely not the video card; I bought an extra 2GB of RAM and things got much, much better.