I've mentioned in a couple of posts that I'm pretty amazed with the quality of the "Retina Display" on the new MacBook Pro. Of the four computers I use, the rMBP, an iPhone 4S, a "new" iPad and a Mac Mini, only the Mini does not now have a double-density screen as it is connected to our HD TV. Regardless of my clear preference for Apple computers, after a month of using these screens near exclusively for my personal needs and having to suffer a cheap 17" flatscreen at work I am convinced now more than ever that our computer displays are about to change forever.
Apple clearly think so, and I would be amazed if in the next year or so if screens of comparable pixel density do not make it onto the entire Apple range. I am pretty sure though, that the other major manufacturers will follow suit in short order (some already offer comparable smartphone screens). Major Linux distros and Windows are likely to implement proper desktop/interface support for screens of these resolutions in forthcoming updates (Windows 8 may already do this, and "ModernUI" likely looks quite sharp at high density already). I don't see that they can afford not to, as consumers will want their interfaces to scale appropriately and look amazing as soon as affordable displays hit the market.
The definition of 'Retina' display has been debated somewhat outside of the Apple community, but it is taken to be the pixel density at which, under normal operation, the individual pixels become indistinguishable. It holds true: the iPhone has the highest density screen and you hold it a few inches from your nose. The iPad is slightly less dense, but you hold it at a more comfortable reading distance, a few inches further from your nose than the iPhone. The MacBook screen, or a desktop display, will generally be a foot or more away from your face during general use and is the lowest density of the three. oddly enough, and likely thanks in part to some neat rendering tricks like antialiasing, the MacBook screen actually has the most noticeable improvement over it's previous non-retina peers.
It may sound trite, maybe you think I'm being a hopeless fanboy, but I wouldn't go back to using a standard density screen now. Other screens are ugly - in some cases almost offensively so. The higher density renders text as well as print! Text is probably the single biggest gain - it really looks amazing and is a joy to read. When some manufacturers began talking about 4000 resolution TVs a year or two ago it sounded somewhat gross, but on a 27-30" screen that's your ballpark. As manufacturers look at building displays like that for all of your big screens the manufacturing costs will drop. The dominos are in a line.
You will agree with me, and it may be a year or so before you do, but you will.