I own 2/3/4 versions of ipad so I could compare I guess. Just got mine in no lines Princeton store, including smart leather cover. If you are close just go there, all models and empty store. Picked up both black or silver black for ipad air. 32gb wifi. Easiest pickup since ipad2!
First impression - it is amazingly thin and light, also small. Will fit much smaller bags while travel which is great. Speed is about same as iPad4, I can't see much improvement yet in speed, same as with mine iphone5S. Sound is better playing movies, touchscreen is same sensitive, bright and sharp as ipad4/3. Wifi test showing same speed as mine iPad4, so no improvement or very minimal
Smart cover is great, thin and well made, one problem it is not holding iPad well in standup position, needs bit adjustments with hands. I believe it is shorter than old one, that is why. Overall I am happy, two weeks without ipad is tough 
First impression - it is amazingly thin and light, also small. Will fit much smaller bags while travel which is great. Speed is about same as iPad4, I can't see much improvement yet in speed, same as with mine iphone5S. Sound is better playing movies, touchscreen is same sensitive, bright and sharp as ipad4/3. Wifi test showing same speed as mine iPad4, so no improvement or very minimal