First, let me say I've purchased a lot of Apple products over the years and have loved every one, starting with the "dome" iMac and original osx. The rMBP is the first time I regretted a purchase.
The display IS amazing, much like the feeling you get using the new iPad. But that's all you can really say about it - there's little about this computer that adds real value to my work, in 2 important areas.
The Screen
As an avid graphic designer, I was excited about all the screen real estate I could use in 1920 x 1200 mode. But being hunched over and squinting while editing documents in InDesign just wasn't the productivity boost I was hoping for. I'd MUCH rather be plugged in to my 27' display, with it's lower resolution and all, being able to lean back and work in a more relaxed state. I suppose the hi res would come in handy if I was sandwiched in a corner at Starbucks all day, but that just sounds miserable. And when I bumped up the size for true retina, the Adobe apps just look terrible. Especially the text rendering in InDesign. I know eventually Adobe will tackle this - probably 2 years from now. Don't get me wrong - it's a great display to look at - it just isn't that important to me personally. If its the only screen you own, and you work on a laptop all the time, then it's great.
Speed
So I own a 2009 MBP, and I added an SSD to it a year and a half ago. It seems to me that the SSD is the great equalizer. I just didn't feel any faster on the new machine than on my crusty Core 2 Duo. I might feel differently if I used heavy processor apps, but I think for most EVERY daily use case, the SSD makes processor speed almost irrelevant. I remember when I put in the SSD I felt like I bought something 10 years ahead of my time. Using the rMBP, it's like I'm trying to talk myself into believing it's a LITTLE faster. And it's 3 years newer!
Anyway, those are my thoughts. The folks at the Apple Store were shocked when I brought it in, couldn't believe I was returning it. I know it's a hot item, and it really is fun to look at, just overrated in my opinion.
I remember my first Mac, being amazed that I could edit a family movie... Then my first PowerBook, a legitimate notebook I could take anywhere and do real work... And both the 24' and 27' displays were amazing upgrades for producing graphic design. I just don't see how this one is much of a leap, though I DO appreciate Apple's lead in developing better and better displays. Maybe I just need to wait for the software to catch up.