My MBP Retina arrived on July 5th and I've had a few days to play with it. All of the supported modes look fantastic provided the app utilizes Core Text for drawing (the latest font system for OS X). I think the 1680x1050 mode looks slightly less crisp than the other modes but compared to all non-retina displays it's still much better. Firefox and BBEdit use other text drawing mechanisms (custom or ATSUI respectively from what I've read) and in those apps text looks pixelated and awful. So much so that I couldn't stand using Firefox any more and switched to Safari. For those apps that use Core Text however the fonts are simply incredible.
At this point most non-Apple apps and virtually all websites use artwork geared for lower resolution displays and as a rule images don't upscale well. This means icons and other graphics in a lot of places are a bit fuzzy. It's not the fault of the machine of course, except insofar as it's way ahead of the technology curve, but it has been at least for me a minor distraction. App and website developers will undoubtedly catch up given time.
I've been using the 1900x1200 scaled resolution for coding and it's sweeeeet. The text is crisp and I've got a lot of room on the screen.
All in all I'm really happy with this machine, the single drawback IMO is that Apple decided not to ship an OS disk with the system. It's my habit to clone my old system onto a new machine whenever I get a new laptop and without a whit of warning I wiped out the MBP's ability to boot from its internal drive. I was able to get things running again with the Internet Recovery option followed by a Migration Assistant-based copy (rather than a Disk Utility-based restore) but it took hours and was a major hassle. So much for Apple's vaunted "we build what the customer would love" philosophy.
That unfortunate bit of unpleasantness aside, the system is still outstanding in the extreme. A few of our developers who've been using 17" MBPs are very happy with the new systems and feel like they didn't lose any screen real estate.
