1. Obviously the display will be MUCH better. Think RetinaThere's a reason why Lion already has Retina support built in... because we WILL be needing it.
1. What is "Retina support"?
2. Are you talking about the 3200x2000 wallpapers?
3. Retina displays would require resolution independence (which Lion doesn't have unless I missed something in my developer preview). Without it, there is absolutely, 100%, NO way for a retina display in any of Apple's computers.