You can definitely see the difference! Have you even looked at one? Or an iPhones retina screen? Big big difference.
Ditto that addiosamigo. The display is different on the new iPad. I use my iPad to read music scores, on the new iPad the notes are crisp. My music reader recently updated to the new iOS and on the new iPad the app is very stable. On documents is where I can see the difference. Movies or videos not so much but I suspect that is a delimiter based on the media provided.