Hi John,
I have the 11", maxed out version (1.6 GHz processor, 4 GB memory and 128 GB SSD disk)
I like it very much, it breezes through the photos in PM real fast once you have ingested them onto your SSD disk.
As it only has USB2 ports for your card reader, a MacBook Pro with a firewire card reader is of course faster to use.
The MBA display is good and the high resolution means that you have as much screen real estate as on the 13" MBP.
The small size and light weight of the MBA means that it can easily slip into the camera bag but the small size of the internal SSD disk means you normally must carry one or two extra hard disks for the image files if you are on an extended assignment.
-Per