It has a slightly faster processor (don't be fooled by "1.3GHz", the MBA's top CPU speed is 2.6GHz) but there's a 500GB non-solid-state hard drive, it's heavier, the graphics are older, and it has a lower-resolution screen. Why would anyone want it?
Although the fact it's Apple-made is probably more important, since they'll have made sure it works.
At which point the SSD and Retina display sound nice, but that other stuff seems like it's going to a pain in the neck on a daily basis.
Remember when the iMac was the first USB-only computer, and had no floppy drive? Both were really unpopular at the time.
(Lack of Kensington is stupid though, I'll agree on that.)
The only downside is on Linux you have to reboot if you unplug the ethernet, but apparently that's being improved in 3.15.
RHEL 7 will be a problem then, I assume, as it seems to be based on 3.10?