I haven't gotten a rMBP. Yet. I use a 2012 13 inch MBA on a regular basis. I think the screen on that is really sharp (LG) and the system overall is as powerful as I'd ever imagine having (i7 2.0, 8GB RAM, 256GB SSD). I don't know how much of an improvement a 13 inch rMBP would really be over this MBA.
I don't care about upgrading in the future. I've had PCs since the first IBM PC in the stone age, and I have upgraded them maybe twice. I get a config that will last me for as long as I can see into the future and stick with that. And I don't buy into this line of thought which says that I have to have the ability to add more RAM in the future because apps are on a linear growth curve and will eat up all the RAM you have now in just another year or so. Any app that does that is a resource pig and I won't buy it.
I don't care about resell value. I've never sold a PC, and have no intention to. I typically use them until they keel over and go belly up. But PCs in recent years have become more reliable, so it's more that I get tired of the OS (STUPID VISTA!) and want to move to a more forward-thinking platform. Hence, the MBA and now ML.
But I can't keep on borrowing the MBA (from my significant other) all the time, and I can't take this Vista disaster much longer. So, I will have to make a choice soon, and that will be between the new 13 inch rMBP, another 13 inch MBA, or a 15 inch rMBP. The one thing I've found with the MBA that I haven't been happy with is the smallness of the text on the screen. My eyes are evidently too used to the 15 inch screens I've had on my recent systems, and I don't know if I'd be happy with a 13 incher full time, even a Retina. In fact, especially if it's a Retina, because I'd want to play with the resolution to optimize screen real estate, which would make some things smaller and even harder to see. That might not be so bad on a 15 inch screen.
But the main thing that kept me from buying a rMBA on day one was the price. Factor in tax and Apple Care, and that gets pretty hard to justify. I don't know if a Rev B of the rMBP would be any less expensive, so waiting until next year doesn't make sense if price is the key factor here.
I just wish the rMBP didn't cost more than my first car did. Oh, sorry... my first 3 cars. COMBINED.