I think the rMB could definitely be my only machine - right now I have a 2011 13" MBA, which is just a tad slower than the rMB. My main concern is the ability to use an external monitor. Right now I plug the MBA into a 27" Apple Thunderbolt Display, which is wonderful with the mini displayport and MagSafe connectors. It seems that at the moment, the rMB will have to drive a HDMI display with the Apple adapter, and the power brick plugged into the adapter along with a USB-A connector for wired keyboards and/or external drives. This solutions seems like it would work fine, but it's not as elegant as the Thunderbolt Display setup. Apple surely must have some sort of USB-C Display in the works; they haven't updated the Thunderbolt Display since the days of original MagSafe power connector.