I will say that the RMBP is faster than the MBAs if you run it at base settings for the screen. If you just don't care that you are getting only 1440x900 in screen real estate, it's awesome. The maximum speed for while it's plugged into the wall is also excellent. If you constantly have it plugged into the wall, you'll kill your battery in about 1 year so I hope you purchased Applecare. If you're mobile in the field, the extra speed of having flash storage and MBP level processing is excellent but IMO it's still lacking the full potential speed. Also Photoshop and non-retina apps look pretty bad on the screen and don't give you a realistic view of what's really going on with your photos. If you're an Aperture or FCPX user, the Retina resolution is great but it also doesn't give you any extra screen real estate. Right now, the largest issue that I had was with slowdown when you're running multiple layers in PSCS6 at the higher base res that can be hacked in. The text is also abysmally small so you can hardly read it. While you do get a true 1:1 on the screen at this point, the GPU is choking on it and the lags get to be pretty bad if you go beyond 15 layers. Maybe I had a bunk machine but from other users I've checked with, it seems to be consistent across the board. I also can't justify carrying a 15 inches anymore so I switched down to 2 Z-spec 2012 11-inch MBAs for dual processing in the field with a Z-spec iMac and Mac Pro for in-studio processing.
How's the Pegasus R6? I was afraid to get one due to the horror stories of multiple drive failures within the first few months and the long wait times for getting replacement drives. Is it stable for you?