I stopped by the Apple store today, and I'm very surprised I didn't buy anything.  That said, the rMBP is a nice machine.  The display is gorgeous.  But I was not drooling over it.  I noticed some jerkiness in scrolling, which really bugged me.  Still a very nice machine.  Then I spent some time with the 27" iMac.  I loved it.  However, I really wish websites were optimized to take advantage of the screen width.  It looks weird to have them centered.  Zooming in can make a nice difference but some of the graphics then get pixelated, which is the only time I would find myself wanting a retina display.  The 21.5 is nice but I would want more screen real estate.  So, it doesn't seem like there's a perfect machine for me right now.  A 21.5" iMac with retina would be pretty great.  At the same time I really want the 27" iMac but feel like a complete sucker buying a machine 440+ days into its cycle.  Bah.