I've just cancelled an order for a rMBP, and am seriously considering an Air.
This machine will be a direct replacement for my aging iMac (2006).
Portability is not a key consideration, but I have reluctantly come round to the conclusion that I need 512GB local storage, making it a straight fight between the fully-loaded 13" Air and the higher spec rMBP.
The difference is around £500 GBP.
Having become used to a retina display on my iPhone and iPad, it seems the rMBP might be the way to go, if only for future-proofing (this machine needs to last at least 5 years), but I was pretty impressed with the resolution of the Air when I fooled around with one today even that is a big improvement in resolution from my iMac, and makes stepping down from 20" to 13" appear tolerable.
I'm not a "pro" user I mainly use my Mac for iTunes, Safari, bittorrent and video conversion (using Elgato Turbo 264HD), so kinda feel that a MacBook Pro would be overkill.
The alternative to both is sitting tight and waiting for the new iMac, but I'm increasingly convinced that desktops have had their day.
What do you reckon?