Just pulled the trigger on a 2012 MBA spec'd with 8GB of ram. Was tempted to splurge and get the rMBP but I figure the money I save will go towards a nice NAS for the household.
Heads up for fellow new MBA buyers, OWC just got the new SSD modules made with the new connectors so heres your chance for an upgrade.
SSD for MacBook Air 2012 - OWC Mercury Pro Aura Express Sandforce Driven