I use an 11in MBA (circa 2011) to travel, have an iMac 27 (2011) on my office desk and an older 15" MBP which rarely leaves my home office. I am thinking the retina 15 MBP could serve as a single computer to replace all these, with external monitors and backup drives at suitable locations. Compared to the MBA there is a weight penalty, but lessened somewhat with this unit. This is balanced by the overhead of maintaining three systems. Anyone else out there made or have advice on this type of transition?