Dustin Curtis:

There has been a lot of discussion about the pixel density in iPhone 4’s Retina display, but most of those discussions are missing the point. The Retina display isn’t revolutionary because of pixel density — some Android phones have featured almost 300ppi for months. iPhone 4 is revolutionary because it has increased interface definition.

Yup. If you’re doing it right, you’re quickly finding yourself using the concept of a “pixel” less and less, especially on iOS devices.