Holo dark and light

A lot of work has gone into the UI for Ice Cream Sandwich, and Google has decided that manufacturers who want to have access to the Android Market will now have to let it shine -- the Holo theme, in its unmodified form, is now a requirement for devices that wish to use the Android Market. 

Calm down, calm down -- manufacturer skins like Blur and Sense will still be around. (You were worried about them, we know.) But menus, widgets, and settings dialogs will now have to follow the standards set up in Android 4.0 and above.

This means a lot to app developers.  Having a standard set of UI elements to draw from makes applications look and feel more integrated into the operating system, and now that everyone will have to use the same base they don't have to worry about coding their own.  Adam Powell, Android framework engineer, says:

Before Android 4.0 the variance in system themes from device to device could make it difficult to design an app with a single predictable look and feel. We set out to improve this situation for the developer community in Ice Cream Sandwich and beyond.

Nice work, fellows.  The Holo UI is unique, and stunning.  Let it shine!

Source: Android Developers Blog