With the iPhone 4, the Retina display's resolution is so high that most people cannot distinguish the pixels from one another (supposedly). If this is the case, do apps that support the Retina display still need anti-aliasing to make fonts and images smooth, or is this no longer necessary?
Edit: I'm interested in more detailed information. Started a bounty.
The resolution at which the eye/brain will detect a discontinuity or stair edge is higher than the resolution at which it can resolve individual pixels. The Retina display appears to be high enough for the latter.
But throw in image animation, hand motion, vehicle vibration, imperfect eyesight, display reflections, et.al. and you may have to experiment to determine whether the former makes any difference in your particular application.
At some point the number of DPI is high enough that a "pixelated" line at such a high resolution will still look smooth. I'm not sure if Retina would be it. For application like gaming, if you had a screen with 300 DPI or more, you would not need anti-aliasing for geometry. (though things like textures and sprites would still need it since when you approach objects in a 3D world (or even look at them from different angles) the textures are stretched or shrunk)
Here's a great article on the subject: http://gamintafiles.wordpress.com/2012/03/12/when-anti-aliasing-is-no-longer-needed/