Retina Macbook Pro: fonts look terrible
Apple announced in the 2012 WWDC Keynote that applications needed to be updated to take advantage of the Retina display. Apps calling Apple text display APIs may benefit from Apple's improvements thereto without needing to be updated. Apps that use routines that had not been updated would use pixel doubling, which would make their text display using half the resolution of apps properly designed for the new machine.
Apple, naturally, has updated many of their apps, but the versions of third-party apps on the machine you tried had likely not been updated.
There is little you as an end user can do to make the programs render text better, but if you are using products from reputable vendors who update their products frequently, such updates should be released soon to take advantage of Apple's new HiDPI settings.
Apps that use Apple's APIs to draw text will have crisp text. Apps that draw the text in other ways (such as using an off-screen buffer) or render everything to an image before displaying it will have fuzzy text.
One mail client in particular (I believe it's Sparrow) has both crisp and fuzzy text in the same window: the email list is custom-rendered and has fuzzy text, while the message view is using a standard text component and has crisp text.
You'll have to wait for those apps to be updated with support for the display.
Apple's updated most of theirs (though not iWork) Some third-party developers have as well, but I'd expect Microsoft and Adobe to take their time.
The simple solution is to wait until the applications are updated.
I have a MBPR. I use Parallels with Visual Studio, Office, WebMatrix, and some other applications on Windows 7. The text looks great on the max scaled display setting. An update to parallels has been released to make things look better: http://reviews.cnet.com/8301-13727_7-57470587-263/parallels-update-brings-retina-display-support/
I was so impressed by the performance of the 2.6/16/512 that I decided to take it back for the 2.7/16/768. Being able to swipe between VS and XCode is super convenient for when I'm developing iOS apps that talk to a ASP.NET Web API. There is plenty of screen real estate with the scaled mode. Personally, I do not like the "Best for Retina" setting, because it feels like a netbook display.
Office for Mac 2011 looks pretty awful, as of right now.