A lot of talk here about tiny text and slow performance with extra pixel counts that retina will bring. Have some faith that Apple will deliver something extraordinary. Will we need powerful GPUs to handle the extra pixel pushing to drive 2D GUI-driven tasks? Somewhat. To handle the extra work in 3D/full screen apps? Certainly. I highly doubt Apple would proudly announce "New sparkling, crisp, unmatched superior displays, now with shearing, laggy graphics and tiny, unreadable text!"
The last time the industry focused this much on display resolution was the mid 90's, when the VGA standard was giving way to the SVGA and then XGA that is still technically in use today. Monitors were tube/analog then, so the race from 13" to 15" to 17" was on, as video cards were now capable of displaying 1024x768 on the same screen as the 640x480 that everyone was accustomed to. Text became totally unreadable as people tried higher resolutions. But then, the OS matured to compensate for this. It became a simple matter for the user to change the default / system font sizes for different resolutions, obviating this problem.
I think if retina is really here for the entire Mac line, Apple will include support at the OS level to easily change font size as resolutions are increased. It would actually be somewhat trivial to calculate physical dimensions into it, so that as PPI increased, the fonts would scale to be the same physical size.
And Apple will make sure that the GPUs are beefed enough to AT LEAST give us equivalent performance to the 2011 GPUs running on their standard resolutions, if not faster for a boost in framerate at retina resolution.
Only time will tell.