I take it back, there IS a big difference. When I first started using the iPhone 4 I didn’t notice much difference in the screen until I put it side by side next to my old iPhone and I loaded up a website. The text on my iPhone 3Gs screen looked blurry and gray compared to the very sharp and black text on the iPhone 4 screen. I was very surprised and just like that my iPhone 3Gs screen started looking out dated.
One downside to this sharp high resolution screen is that it makes icons and apps seem low res. That should go away once everyone starts making their apps iOS4 compatible.
The screen on the iPhone I got doesn’t have the yellow spots that have been talked about in the media recently but even if it did it’s not really a big deal. Both Gizmodo and Endgadet have reported that the yellow spots are just screen adhesive that disappears after a few days.