Just had my motherboard replaced after a video card failed yesterday. Got vertical striped lines on the screen and a quick phone call to Dell confirmed it was the graphics card. That Dell employee and the engineer who replaced it today also confirmed this is a known issue with the model. See message boards for more of the same.
Hopefully this helps you decide whether to extend your existing next-day warranty before it runs out. Mine would have expired early March but I'll be extending now. According to the engineer, his highest percentage of hardware repairs are on this model - "by a long shot", as he put it.