Still beat Samsung's attempt fairly easily.. and hugely on the thinness. Samsung's 10" Galaxy S tablet was lighter and thinner than the Air.. Apple won't let them take the crown for too long.
Battery life should be the exact same.. There's nothing removed other than the gap of air in the display, they may have identified another way to cram the same battery inside a thinner chassis if the air gap wasn't enough to get it to 6.1mm.