I have the 11" 2013 i7/8gb/512gb MBA and will not replace it anytime soon. Very powerful and incredibly compact machine with excellent battery life. Last year I watched movies on it all the way from Newark to Heathrow and still had plenty of power left afterwards.
The 802.11ac wifi is great if you have a compatible router (I have an Airport Time Capsule). The Blackmagic disk test reports about 60 MBytes/Sec copying files to my Mini using the MBA with 802.11ac (the Mini is on gigabit ethernet). Compare that to my previous 2011 MBA that only had USB 2.0. A direct connected USB disk only got about 35 MBytes/sec on that machine. Also great for streaming video from the mini (running iTunes home sharing). I can scrub through movies just like they were on a local disk.