Why spend the extra $150 for a GTX 280 if your Intel integrated GPU works just right?
If you can answer that question, you know why you should pay the extra for iPad 2.
Personally after watching how the 3G iPhone (with its inferior hardware) got thrown to the wolves later in its life (with almost unusable iOS updates), I wouldn't want the half powerful iPad. I plan to buy the iPad 2 next week for this reason.
The only reason the 3G lacks compared to anything after it is because of its graphic processor (or lack there of).
I can get a gen 1 ipad now new for about $350. Should I? What is so compelling 'other' than the camera, which I won't use on the ipad.