This review over at Robservatory is one of the best I've seen.
In a nutshell, the new machine crushed the other two—nearly eleven hours remaining, against 2.5 for the old Air and just over six for the MacBook Pro. The short run time for the 2012 Air, with its smaller 35 watt-hour battery, isn’t overly surprising (though 3.5 hours of total usage time is quite short). The 2013 MacBook Pro, though, has a 50 watt-hour battery…yet the new Air’s smaller 35 watt-hour battery has no trouble outlasting it.
Rob goes through pretty much everything I'd care about: the bulk, the power cord, the keyboard, battery life, and the performance, all in comparison with two other well known Apple notebooks. They keyboard is slightly louder. The notebook is almost as small as an old 11 inch model, and the performance is great. This seems like a landmark release for Apple.